Here is another device with Tuya CBU module, here is the AliExpress listing for it - It is based around CHT8305 sensor but it has a GN6932 a multi 7 segment display driver. This is a fast teardown with some basic info, more to come soon. Also attached is the dump from the working device if that...

I will add a calibration function today. I confused drivers. CHT8305 indeed lacks calibration.

Here is the capture from the cold boot from PulseView (aka Sigrok) from the 3 data lines, DIN, CLK and STB. 6 DIN Data Input Serial data input on clock rising edge, low bit first. 7 CLK Clock input Input/output serial data on the rising edge of the clock 8 STB Chip select Initializes serial interface on rising or falling edge

Just a quick translation from the datasheet of the LED driver: GN6932 is a special circuit for LED (Light Emitting Diode Display) drive control, which integrates MCU digital interface, data lock memory, LED high voltage drive. This product has excellent performance and reliable quality. Mainly used in multi-segment display driver. Its main features are as follows: ● Using power CMOS technology ● Display mode (8 segments×16 bits) ● Brightness adjustment circuit (8-level adjustable duty cycle) ● Serial interface (CLK, STB, DIN) ● Oscillation mode: RC oscillation (450KHz±5%) ● Built-in power-on reset circuit ● Package form: SOP32

This is a very interesting device. I'd rather expect it to be TuyaMCU based, but it doesn't look like it. Are you able to check where is the CHT8305 connected? CHT8305 driver is already in OpenBeken, is it working on this device well? The 2MB backup can be restored anytime, although for the new flash tool you may need to rename the dump and put it into the firmware directory.

Yes I can: CHT pin 1 (SDA) -> CBU pin 4 (P22) CHT pin 6 (SCL) -> CBU pin 3 (P20) Alert pin is NC(?!?) And the CHT is working, Added after 14 [minutes]:Just to confirm renamed backup written and working. In my case I renamed it to OpenBK7231N_QIO_1.15.xxx and the flasher did write and device is in the original state. BTW consider adding backup naming and writing option to flasher.

That's good news. So we need a GN6932 driver. Here's an English translation of GN6932 datasheet: GN-Semic-G...-CN.en.pdf (841.94 kB)You must be logged in to download this attachment. Maybe we could use previous drivers as a reference and write a new one:

I can provide you with the HW info that you need as the SW is the more time consuming for me (because work), as you can notice I write usually after midnight I'll update the first post for CHT config and if you need anything more from me let me know.

Which GPIO are used for GN6932? I will give you the initial test code tomorrow so we can check if the GN6932 reacts in any way. I haven't looked at your capture yet, only datasheet.

CBU P15 -> DIN (GN69320) CBU P17 -> CLK (GN69320) CBU P28 -> STB (GN69320) As I understand DIN is the data sent from CBU, STB is something like chipselects pin, everything else I would have to read the datasheet a bit better. Added after 2 [minutes]:From Tuya datasheet: 20 P17 I/O Common GPIO, which can be reused as SPI_MISO (Correspond to Pin 14 of the IC) 21 P15 I/O Common GPIO, which can be reused as SPI_CS (Correspond to Pin 13 of the IC) I'll try tomorrow to get some captures form logic analyzer and parse data as SPI and give you the results.

Thank you, the basic protocol is the following: Code: C / C++Log in, to see the code but one can write multiple bytes if STB does not go high: Code: C / C++Log in, to see the code The flowchart requires sending 3 commands: setup command, cmd +data, turn on command. first setup command, single byte, 0x40 is 100 0000: Second command has multiple bytes, it's address command + data bytes: 0b1100 0000 is 0xC0. Third command is 0x8F which is 1000 1111: Here is what I come up so far: Code: C / C++Log in, to see the code I will push it to the source in the morning so you can get binaries and test. Curent version just sends random segments data.

Some more info from observing the HW, which can possibly influence the data format set. Added after 12 [minutes]:The data sheet and the data transfer on the board corelate, but configuration depending not all bytes (my guess GRID registers) are used. Here is the short snippet of the data capture from the logic analyzer and decoded as MAX7219. You can load the previously attached capture into PulseView and have a clearer picture about the data transfer structure that is based on this specific configuration.

[BK7321N] Generic USB powered thermostat and humidity sensor with LED display - CBU module

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CBU pin mapping for CHT8305 and GN6932
#1 20535534 11 Apr 2023 23:31

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CBU pin mapping for CHT8305 and GN6932
Post #1 20535534 11 Apr 2023 23:31

Here is another device with Tuya CBU module, here is the AliExpress listing for it - https://shorturl.at/sJVZ6

It is based around CHT8305 sensor but it has a GN6932 a multi 7 segment display driver.

This is a fast teardown with some basic info, more to come soon. Also attached is the dump from the working device if that is of any help and datasheet for that LED driver.

EDIT:
To make the temp sensor working in the config menu set:

CHT pin 1 (SDA) -> CBU pin 4 (P22)
CHT pin 6 (SCL) -> CBU pin 3 (P20)

Led driver configuration:

LED driver pin 6 (DIN) -> CBU pin 21 (P15)
LED driver pin 7 (CLK) -> CBU pin 20 (P17)
Led Driver pin 8 (STB) -> CBU pin 17 (P28)

Button configuration:

Button -> CBU pin 1 (P14)

EDIT: added AliExpress listing.

Attachments:

GN-Semic-GN6932_C265476.pdf (554.82 KB) You must be logged in to download this attachment.

readResult_BK7231N_QIO_2023-11-4--22-47-16.bin (2 MB) You must be logged in to download this attachment.

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#2 20535550 11 Apr 2023 23:50

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Post #2
20535550 11 Apr 2023 23:50

Here is the capture from the cold boot from PulseView (aka Sigrok) from the 3 data lines, DIN, CLK and STB.

6 DIN Data Input Serial data input on clock rising edge, low bit first.
7 CLK Clock input Input/output serial data on the rising edge of the clock
8 STB Chip select Initializes serial interface on rising or falling edge

Attachments:

cold boot org FW.rar (19.62 KB) You must be logged in to download this attachment.

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GN6932 LED driver datasheet translation
#3 20535551 11 Apr 2023 23:53

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GN6932 LED driver datasheet translation
Post #3 20535551 11 Apr 2023 23:53

Just a quick translation from the datasheet of the LED driver:

GN6932 is a special circuit for LED (Light Emitting Diode Display) drive control, which integrates MCU digital interface, data lock
memory, LED high voltage drive. This product has excellent performance and reliable quality. Mainly used in multi-segment display driver.
Its main features are as follows:
● Using power CMOS technology
● Display mode (8 segments×16 bits)
● Brightness adjustment circuit (8-level adjustable duty cycle)
● Serial interface (CLK, STB, DIN)
● Oscillation mode: RC oscillation (450KHz±5%)
● Built-in power-on reset circuit
● Package form: SOP32

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#4 20535569 12 Apr 2023 00:22

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Post #4
20535569 12 Apr 2023 00:22

This is a very interesting device. I'd rather expect it to be TuyaMCU based, but it doesn't look like it. Are you able to check where is the CHT8305 connected?

CHT8305 driver is already in OpenBeken, is it working on this device well?

The 2MB backup can be restored anytime, although for the new flash tool you may need to rename the dump and put it into the "firmware" directory.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
If you like my work, support me at: https://paypal.me/openshwprojects

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CHT8305 wiring and backup restore confirmed
#5 20535581 12 Apr 2023 00:55

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CHT8305 wiring and backup restore confirmed
Post #5 20535581 12 Apr 2023 00:55

p.kaczmarek2 wrote:
This is a very interesting device. I'd rather expect it to be TuyaMCU based, but it doesn't look like it. Are you able to check where is the CHT8305 connected?

CHT8305 driver is already in OpenBeken, is it working on this device well?

The 2MB backup can be restored anytime, although for the new flash tool you may need to rename the dump and put it into the "firmware" directory.

Yes I can:

CHT pin 1 (SDA) -> CBU pin 4 (P22)
CHT pin 6 (SCL) -> CBU pin 3 (P20)
Alert pin is NC(?!?)

And the CHT is working,

Added after 14 [minutes]:

Just to confirm renamed backup written and working.

In my case I renamed it to OpenBK7231N_QIO_1.15.xxx and the flasher did write and device is in the original state.

BTW consider adding backup naming and writing option to flasher.

If you like my work, support me at: https://paypal.me/openshwprojects
#6 20535591 12 Apr 2023 00:55

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Post #6
20535591 12 Apr 2023 00:55

That's good news. So we need a GN6932 driver.
Here's an English translation of GN6932 datasheet:
GN-Semic-G...-CN.en.pdf (841.94 kB)You must be logged in to download this attachment.

Maybe we could use previous drivers as a reference and write a new one:
https://github.com/openshwprojects/OpenBK7231T_App/blob/main/src/driver/drv_tm1637.c
https://github.com/openshwprojects/OpenBK7231...p/blob/main/src/driver/drv_max72xx_internal.c

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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#7 20535593 12 Apr 2023 00:59

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Post #7
20535593 12 Apr 2023 00:59

I can provide you with the HW info that you need as the SW is the more time consuming for me (because work), as you can notice I write usually after midnight

I'll update the first post for CHT config and if you need anything more from me let me know.

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#8 20535610 12 Apr 2023 01:51

p.kaczmarek2 p.kaczmarek2

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Post #8
20535610 12 Apr 2023 01:51

Which GPIO are used for GN6932?

I will give you the initial test code tomorrow so we can check if the GN6932 reacts in any way.

I haven't looked at your capture yet, only datasheet.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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CBU pin mapping to GN69320 SPI signals
#9 20535616 12 Apr 2023 02:07

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CBU pin mapping to GN69320 SPI signals
Post #9 20535616 12 Apr 2023 02:07

CBU P15 -> DIN (GN69320)
CBU P17 -> CLK (GN69320)
CBU P28 -> STB (GN69320)

As I understand DIN is the data sent from CBU, STB is something like chipselects pin, everything else I would have to read the datasheet a bit better.

Added after 2 [minutes]:

From Tuya datasheet:

20 P17 I/O Common GPIO, which can be reused as SPI_MISO (Correspond to Pin 14 of the IC)
21 P15 I/O Common GPIO, which can be reused as SPI_CS (Correspond to Pin 13 of the IC)

I'll try tomorrow to get some captures form logic analyzer and parse data as SPI and give you the results.

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GN6932 command sequence and multi-byte write protocol
#10 20535619 12 Apr 2023 02:25

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GN6932 command sequence and multi-byte write protocol
Post #10 20535619 12 Apr 2023 02:25

Thank you, the basic protocol is the following:

Code: C / C++
Log in, to see the code

but one can write multiple bytes if STB does not go high:

Code: C / C++
Log in, to see the code

The flowchart requires sending 3 commands: setup command, cmd +data, turn on command.

first setup command, single byte, 0x40 is 100 0000:

Second command has multiple bytes, it's address command + data bytes:

0b1100 0000 is 0xC0.
Third command is 0x8F which is 1000 1111:

Here is what I come up so far:
Code: C / C++
Log in, to see the code

I will push it to the source in the morning so you can get binaries and test. Curent version just sends random segments data.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
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Logic analyzer capture decoded as MAX7219 data
#11 20535915 12 Apr 2023 11:27

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Logic analyzer capture decoded as MAX7219 data
Post #11 20535915 12 Apr 2023 11:27

Some more info from observing the HW, which can possibly influence the data format set.

Added after 12 [minutes]:

The data sheet and the data transfer on the board corelate, but configuration depending not all bytes (my guess GRID registers) are used.

Here is the short snippet of the data capture from the logic analyzer and decoded as MAX7219. You can load the previously attached capture into PulseView and have a clearer picture about the data transfer structure that is based on this specific configuration.

Attachments:

test.txt (579.08 KB) You must be logged in to download this attachment.

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Bit order swapped in SPI display commands
#12 20535970 12 Apr 2023 11:52

p.kaczmarek2 p.kaczmarek2

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Bit order swapped in SPI display commands
Post #12 20535970 12 Apr 2023 11:52

I haven't loaded it yet, but your text file looks very interesting.

But it seems that bit order is swapped!

There is basically that:
Code: text Expand Select all Copy to clipboard
17130098-17130262 SPI: MOSI transfers: 02 17130279-17132867 SPI: MOSI transfers: 03 66 60 DA F2 60 FC FC FC 60 F1 C0 00 00 00 00 00 17132885-17133038 SPI: MOSI transfers: F1

0x02 is a first command. It sets the normal mode and auto increment.

This fragment:
Code: text Expand Select all Copy to clipboard
17130279-17132867 SPI: MOSI transfers: 03 66 60 DA F2 60 FC FC FC 60 F1 C0 00 00 00 00 00

it's first 0x03, the address setting, it sets address 0x00

The next part of the data is the segments/grids data. They are using auto address increment and set all in one batch, within single STB tick.
The last part is that:
Code: text Expand Select all Copy to clipboard
17132885-17133038 SPI: MOSI transfers: F1

0xF1 hex is binary 1111 0001, but as I said, you have swapped endiannes, so it is in fact this:

It sets the brightness and enables the display.

Your packet dumps are very helpful, I will try to push the test driver code to repository today so you can flash OBK and try it. For the start, we will set random segments.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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#13 20536000 12 Apr 2023 12:22

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Post #13
20536000 12 Apr 2023 12:22

Sorry that decoding was done as MSB-first, I changed to LSB-first and the message is clear.

40
C0 66 3F 5B 6D 6F 3F 3F 3F 3F 8F 0F 00 00 00 00 00
8F

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GN6932 test driver and pin mapping added
#14 20536026 12 Apr 2023 13:45

p.kaczmarek2 p.kaczmarek2

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GN6932 test driver and pin mapping added
Post #14 20536026 12 Apr 2023 13:45

Suprisingly enough, it matches well what I've written yesterday, just by basing on the datasheet:

Ok, I will push that test driver in a hour or two, I am looking into door sensors protocol now:
https://www.elektroda.com/rtvforum/topic3937723-90.html#20535974

Added after 55 [minutes]:

This protocol looks the same as TM1637, except the addition of the STB pin and lack of the ACK. One could say that GN6932 is SPI version of TM1637 ?

Anyway, I added test code:
https://github.com/openshwprojects/OpenBK7231...mmit/0b8a78fa2b6420cf1a2af3cc629b15c603681c97
It assumes pin indices:
Code: text Expand Select all Copy to clipboard
int g_clk = 17; int g_stb = 28; int g_din = 15;

Usage:
1. enter command startDriver GN6932
2. enter command GN6932_TestAddressIncreaseMode , random segments should lit up.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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GN6932 command changes bus pattern; byte order corrected
#15 20536357 12 Apr 2023 16:51

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GN6932 command changes bus pattern; byte order corrected
Post #15 20536357 12 Apr 2023 16:51

It does work, there is a changing pattern with every GN6932_TestAddressIncreaseMode command, here is the analyzer screenshot (sorry decoding is wrong by my mistake it is MSB first should be the other way around)

tested with 680 build.

EDIT:
corrected byte order

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#16 20536367 12 Apr 2023 17:01

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Post #16
20536367 12 Apr 2023 17:01

For anyone reading, here's the code from example above:
https://github.com/openshwprojects/OpenBK7231...mmit/6ed64af07cef12ebb25cf6b8a83497b02c730f99
https://github.com/openshwprojects/OpenBK7231...cf6b8a83497b02c730f99/src/driver/drv_gn6932.c

I will add ability to change dimmer level (3 bits can determine brightness) soon.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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#17 20536418 12 Apr 2023 17:42

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Post #17
20536418 12 Apr 2023 17:42

Brightness control does work!

Build 681

Enter in command line:

1) GN6932_TestAddressIncreaseMode
2) GN6932_Dimmer 1 3 - syntax is GN6932_Dimmer [bOn] [brightness], (bOn is 0 for OFF and 1 for ON, brightness level 0-7)
3) GN6932_TestAddressIncreaseMode - to apply changes (also lit characters will change)

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Merged TM1637 and GN6932 driver with test commands
#18 20536515 12 Apr 2023 18:49

p.kaczmarek2 p.kaczmarek2

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Merged TM1637 and GN6932 driver with test commands
Post #18 20536515 12 Apr 2023 18:49

I have pushed merged TM1637 + GN6932 driver.
https://github.com/openshwprojects/OpenBK7231...mmit/3b25aee97370775559e279f879bb016c0f1304fd
It currently uses your pins by default.
Code: text Expand Select all Copy to clipboard
i2c.pin_clk = 17;// PIN_FindPinIndexForRole(IOR_TM1637_CLK, 16); i2c.pin_data = 15;// PIN_FindPinIndexForRole(IOR_TM1637_DIO, 14); i2c.pin_stb = 28;// PIN_FindPinIndexForRole(IOR_TM1637_DIO, 14);

(yes, I know, that's not I2C...)

usage:
1. start and try to print something:
Code: text Expand Select all Copy to clipboard
backlog startDriver GN6932 ; TMGN_Print 0 0 123456 // NOTE: TMGN_Print [Ofs] [MaxLen] // If MaxLen=0, then no lenght limit

Is it printing anything?

2. check brightness changes:
Code: text Expand Select all Copy to clipboard
backlog TMGN_Brightness 5; TMGN_Print 0 0 123456 // NOTE: TMGN_Brightness [Brightness0to8] [bOn] // The bOn is optional, default is 1 backlog TMGN_Brightness 2; TMGN_Print 0 0 123456 backlog TMGN_Brightness 7; TMGN_Print 0 0 123456

Are they working?

3. try to create character codes
Code: text Expand Select all Copy to clipboard
TMGN_Char 0x00 123 // Note: TMGN_Char CharIndex CharCode

This is 7 segment display, I assume.
So we can display: 0, 1, 2, etc etc 9, A, B, C, etc F.
But we need to know which segments are displayed for each letter.
That function can set code for given index.
For example, TMGN_Char 0 123 sets code for 0.
The TMGN_Char 10 33 sets code for A (A is 10)
etc etc.

You can play around it by:
- first use TMGN_Char 0 33 , replace 33 with anything
- then use TMGN_Print 0 0 00000 - does it print proper 0?

You can also do a tricky way and just use character codes from your capture
Code: text Expand Select all Copy to clipboard
40 C0 66 3F 5B 6D 6F 3F 3F 3F 3F 8F 0F 00 00 00 00 00 8F

ok so 3F most likely is 0 here? What was the display showing when you captured that data?
Try:
Code: text Expand Select all Copy to clipboard
TMGN_Char 0 0x3F TMGN_Print 0 0 00000 - does it print proper 0?

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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#19 20536999 12 Apr 2023 22:56

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Post #19
20536999 12 Apr 2023 22:56

Some observations that may help in the future:

Also mask for the front of the unit:

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#20 20537108 13 Apr 2023 00:36

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Post #20
20537108 13 Apr 2023 00:36

Following script should work with both GN6932 and TM1637 and create a simple clock.
Code: text Expand Select all Copy to clipboard
//startDriver GN6932 startDriver TM1637 startDriver NTP TMGN_Clear again: // TMGN_Print offset len value bPadToLenWithZeros TMGN_Print 4 2 $second 1 TMGN_Print 2 2 $minute 1 TMGN_Print 0 2 $hour 1 delay_s 0.1 goto again

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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Working GN6932/TM1637 clock script and grid mapping
#21 20537116 13 Apr 2023 00:47

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Working GN6932/TM1637 clock script and grid mapping
Post #21 20537116 13 Apr 2023 00:47

p.kaczmarek2 wrote:
Following script should work with both GN6932 and TM1637 and create a simple clock.
Code: text Expand Select all Copy to clipboard
//startDriver GN6932 startDriver TM1637 startDriver NTP //edit for your time zone //ntp_timeZoneOfs +2:00 TMGN_Clear again: // TMGN_Print offset len value bPadToLenWithZeros TMGN_Print 4 2 $second 1 TMGN_Print 2 2 $minute 1 TMGN_Print 0 2 $hour 1 delay_s 0.1 goto again

Build 688.
Just to confirm, this is the script that is working for the clock (refer to previous picture explaining GRID placement index starts from 0-8 not 1-9) and seconds are where humidity should be (GRID1 or index 0) for now.

//startDriver GN6932
startDriver TM1637
startDriver NTP
TMGN_Clear

again:
// TMGN_Print offset len value bPadToLenWithZeros
//GRID1_2digits_seconds
TMGN_Print 0 2 $second 1
//GRID8_2digits_minutes
TMGN_Print 7 2 $minute 1
//GRID6_2digits_hours
TMGN_Print 5 2 $hour 1
delay_s 0.1
goto again

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TMGN_Print can map channel values to display
#22 20537575 13 Apr 2023 12:17

p.kaczmarek2 p.kaczmarek2

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TMGN_Print can map channel values to display
Post #22 20537575 13 Apr 2023 12:17

We can use the same approach to map any values from channels to the display. For example, if channel 1 is humidity, then you should be able to do:
Code: text Expand Select all Copy to clipboard
TMGN_Print 7 2 $CH1 1

I am not sure about the scaled values yet. This is because we may have a temperature value like 21.5C stored as 215... I will think about it, but maybe it will just work as is.

I am attaching a C source code for hybrid TM1263/GN6932 driver.
drv_tm_gn_...230412.zip (3.26 kB)You must be logged in to download this attachment.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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Working GN6932 autoexec script for BK7321N display

#23 20537716 13 Apr 2023 15:53

DeDaMrAz DeDaMrAz

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Working GN6932 autoexec script for BK7321N display

Post #23 20537716 13 Apr 2023 15:53

Got it working, that approach worked. Here is the pictures and the script that worked for me. All that is left is the always on LED's.

Script that works for me now on build 688.

 startDriver GN6932
startDriver NTP
ntp_timeZoneOfs  +2:00
TMGN_Clear

again:
// TMGN_Print  offset len value bPadToLenWithZeros
//TMGN_Print 0 2 $second 1
TMGN_Print 7 2 $minute 1
TMGN_Print 5 2 $hour 1
TMGN_Print 2 3 $CH1 1
TMGN_Print 0 2 $CH0 1
delay_s 0.1
goto again

EDIT: confirmed working with Build 691.

Added after 1 [hours] 36 [minutes]:

To conclude this is the working script, I created autoexec.bat and it works as intended.

 startDriver GN6932
startDriver NTP
ntp_timeZoneOfs  +2:00
TMGN_Clear
//adjust brightness if needed (0-7) - default is 7
TMGN_Brightness 7
TMGN_SetBit 9 1 1
TMGN_SetBit 9 2 1
TMGN_SetBit 9 3 1
TMGN_SetBit 9 7 1
TMGN_SetBit 9 0 1
TMGN_SetBit 10 2 1
TMGN_SetBit 10 3 1

again:
// TMGN_Print  offset len value bPadToLenWithZeros
//TMGN_Print 0 2 $second 1
TMGN_Print 7 2 $minute 1
TMGN_Print 5 2 $hour 1
TMGN_Print 2 3 $CH1 1
TMGN_Print 0 2 $CH0 1
delay_s 0.1
//blinking : on the clock
TMGN_SetBit 10 0 0
TMGN_SetBit 10 1 0
delay_s 1
TMGN_SetBit 10 0 1
TMGN_SetBit 10 1 1
delay_s 1
goto again

And a picture to prove it

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#24 20537859 13 Apr 2023 16:00

p.kaczmarek2 p.kaczmarek2

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Post #24
20537859 13 Apr 2023 16:00

Very nice progress! This device seems almost fully supported.

We could try to convert C to F somehow. Maybe use extra channel as a variable. Is temperature in channel 0?
Code: text Expand Select all Copy to clipboard
setChannel 10 $CH0*1.8+32 TMGN_Print 0 2 $CH10 1

Math expressions are supported already, but we also would need to support that extra '1' digit first? Or maybe not... 100F is not a common temperature.

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Script for 100°F display limit and °C conversion

#25 20537947 13 Apr 2023 16:52

DeDaMrAz DeDaMrAz

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Script for 100°F display limit and °C conversion

Post #25 20537947 13 Apr 2023 16:52

This script works up to 100'F, there is also a provision to convert to 'C in the script. Measurement above 100'F requires some logic and multiple changes to work due to current temp reading (without decimal point). Attached are the scripts that you can load to your device.

 startDriver GN6932
startDriver NTP
ntp_timeZoneOfs  +2:00
TMGN_Clear
//adjust brightness if needed (0-7) - default is 7
TMGN_Brightness 7
TMGN_SetBit 9 1 1
TMGN_SetBit 9 2 1
TMGN_SetBit 9 3 1
TMGN_SetBit 9 7 1
TMGN_SetBit 9 0 1
TMGN_SetBit 10 2 1
TMGN_SetBit 10 3 1

again:
// TMGN_Print  offset len value bPadToLenWithZeros
//TMGN_Print 0 2 $second 1
TMGN_Print 7 2 $minute 1
TMGN_Print 5 2 $hour 1
//TMGN_Print 2 3 $CH1 1
//comment upper one line and uncomment the next 4 linet to convert to F and vice versa for C
setChannel 10 $CH1*1.8+320
TMGN_Print 2 3 $CH10 1
TMGN_SetBit 9 7 0
TMGN_SetBit 9 4 1
TMGN_Print 0 2 $CH0 1
delay_s 0.1
//blinking : on the clock
TMGN_SetBit 10 0 0
TMGN_SetBit 10 1 0
delay_s 1
TMGN_SetBit 10 0 1
TMGN_SetBit 10 1 1
delay_s 1
goto again

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#26 20539367 14 Apr 2023 15:07

DeDaMrAz DeDaMrAz

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Post #26
20539367 14 Apr 2023 15:07

It would be good if somebody else can confirm this but I noticed that the CHT sensors are having +2'C offset on them - on at least 3 converted devices. Here is a picture of temperature comparison after more then 3 hours of measurements and stabilizing (k Type probe is inside the housing very close to the CHT)

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#27 20539472 14 Apr 2023 16:47

p.kaczmarek2 p.kaczmarek2

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Post #27
20539472 14 Apr 2023 16:47

It seems that the driver contributor, @dheenhasty , has added a calibrate function already:

SHT_Calibrate
https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/commands.md

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
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SHT_Calibrate not supported on CHT8305 sensor

#28 20539486 14 Apr 2023 16:56

DeDaMrAz DeDaMrAz

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SHT_Calibrate not supported on CHT8305 sensor

Post #28 20539486 14 Apr 2023 16:56

p.kaczmarek2 wrote:
It seems that the driver contributor, @dheenhasty , has added a calibrate function already:

SHT_Calibrate
https://github.com/openshwprojects/OpenBK7231T_App/blob/main/docs/commands.md

That command doesn't work on CHT8305

tried already

Info:SENSOR:DRV_CHT8304_readEnv: Temperature:27.354543C Humidity:19.824522%
Info:MAIN:Time 87358, idle 184978/s, free 73208, MQTT 0(5460), bWifi 1, secondsWithNoPing 1, socks 2/38 
Error:CMD:cmd SHT_Calibrate NOT found (args -2 10)
Info:CMD:[WebApp Cmd 'SHT_Calibrate -2 10' Result] Unknown command
Info:GEN:CHANNEL_Set channel 1 has changed to 274 (flags 0)

Info:SENSOR:DRV_CHT8304_readEnv: Temperature:27.384756C Humidity:19.848936%
Info:MAIN:Time 87447, idle 186866/s, free 61512, MQTT 0(5465), bWifi 1, secondsWithNoPing 1, socks 3/38 
Error:CMD:cmd SHT3X_Calibrate NOT found (args -2 10)
Info:CMD:[WebApp Cmd 'SHT3X_Calibrate -2 10' Result] Unknown command
Info:GEN:No change in channel 1 (still set to 273) - ignoring

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Helpful post

#29 20539583 14 Apr 2023 18:14

p.kaczmarek2 p.kaczmarek2

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Post #29
20539583 14 Apr 2023 18:14

I will add a calibration function today. I confused drivers. CHT8305 indeed lacks calibration.

I am creating multiplatform open source firmware (Tasmota replacement), right now supporting BK7231T, BK7231N, XR809, BL602, W800, W600, LN882H and soon supporting RTL and W701:
https://github.com/openshwprojects/OpenBK7231T
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CHT_Calibrate working with temperature and humidity offsets

#30 20539841 14 Apr 2023 20:43

DeDaMrAz DeDaMrAz

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CHT_Calibrate working with temperature and humidity offsets

Post #30 20539841 14 Apr 2023 20:43

Build 701, CHT_Calibrate is working!!!

Info:SENSOR:DRV_CHT8304_readEnv: Temperature:27.505607C Humidity:17.523460%
Info:MAIN:Time 101, idle 181167/s, free 72976, MQTT 0(6), bWifi 1, secondsWithNoPing 1, socks 2/38 
Info:SENSOR:Calibrate SHT: Calibration done temp -2.000000 and humidity 10.000000 
Info:CMD:[WebApp Cmd 'CHT_Calibrate -2 10' Result] OK
Info:GEN:CHANNEL_Set channel 1 has changed to 255 (flags 0)

this is the final script with everything working (for me)

startDriver GN6932
startDriver NTP
ntp_timeZoneOfs  +2:00
//check the reading of you sensor against a good known and calibrate in this case -2
CHT_Calibrate -2 10 
TMGN_Clear
//adjust brightness if needed (0-7) - default is 7 max
TMGN_Brightness 7
TMGN_SetBit 9 1 1
TMGN_SetBit 9 2 1
TMGN_SetBit 9 3 1
TMGN_SetBit 9 7 1
TMGN_SetBit 9 0 1
TMGN_SetBit 10 2 1
TMGN_SetBit 10 3 1

again:
// TMGN_Print  offset len value bPadToLenWithZeros
//TMGN_Print 0 2 $second 1
TMGN_Print 7 2 $minute 1
TMGN_Print 5 2 $hour 1
TMGN_Print 2 3 $CH1 1
TMGN_Print 0 2 $CH0 1
delay_s 0.1
//blinking : on the clock
TMGN_SetBit 10 0 0
TMGN_SetBit 10 1 0
delay_s 1
TMGN_SetBit 10 0 1
TMGN_SetBit 10 1 1
delay_s 1
goto again

For other users syntax is:
CHT_calibrate [+/- temperature value] [+/- humidity value] you can omit + symbol as that is the default so:
CHT_calibrate -2 10 = change temp-2 and humidity+10 in this case.
(SHT_Calibrate works exactly the same)

Attached are the files that you can uplaod to your LFS

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Topic summary

The discussion focuses on a generic USB-powered thermostat and humidity sensor device based on the Tuya CBU module, featuring a CHT8305 sensor and a GN6932 multi 7-segment LED display driver. Detailed hardware pin mappings were established: CHT8305 SDA to CBU P22, SCL to CBU P20; GN6932 DIN to CBU P15, CLK to P17, and STB to P28. The GN6932 driver was reverse-engineered, revealing it as a serial interface LED driver with 8-level brightness control and SPI-like communication, similar to TM1637 but with an added STB pin and no ACK. A test driver and example scripts were developed and integrated into the OpenBK7231T firmware, enabling display of temperature, humidity, and time with brightness adjustment and segment control via commands like TMGN_Print and TMGN_SetBit. Calibration for the CHT8305 sensor was initially missing but later implemented, allowing temperature offset correction. Newer device models reportedly use the CHT8310 sensor, which is similar but requires updated drivers. Firmware builds sometimes disable the GN6932 driver due to flash size constraints, requiring manual enabling in the configuration. Users shared scripts for clock display and sensor data visualization, including temperature unit conversion between Celsius and Fahrenheit. Additional support and clarifications on command usage (e.g., TMGN_SetBit parameters) were provided, along with links to source code and documentation. The community also addressed static IP configuration during OpenAP mode for device network setup. Overall, the device is now well-supported in OpenBeken firmware with active development on display drivers and sensor calibration.
AI summary based on the discussion. May contain errors.

FAQ

TL;DR: For this BK7231N/CBU USB thermostat, 3 GN6932 lines and “bit order is swapped” are the key clues: use CHT on P22/P20, GN6932 on P15/P17/P28, then script TMGN for temperature, humidity, and time in OpenBeken. [#20535970] Why it matters: This turns a generic Tuya LED thermostat into a locally controlled OpenBeken sensor-display device without relying on Tuya cloud firmware.

Alternative	Sensor or driver	Thread-specific status	Key command or setting
CHT8305	I2C temperature/humidity	Original teardown sensor	SDA P22, SCL P20
CHT8310	I2C temperature/humidity	Seen in newer units	Needs newer OpenBeken support
GN6932	8×16 LED driver	Disabled in some newer builds	`#define ENABLE_DRIVER_TMGN 1`
TM1637/TM1638	Related LED drivers	Similar TMGN command family	`TMGN_Print`, `TMGN_SetBit`

Key insight: The display is not TuyaMCU-driven. OpenBeken can drive it directly when the GN6932/TMGN driver is enabled and the three display pins are mapped correctly.

Quick Facts

CHT8305 wiring found in the device: SDA uses CBU pin 4/P22, SCL uses CBU pin 3/P20, and the alert pin was not connected. [#20535581]
GN6932 wiring found in the device: DIN uses CBU pin 21/P15, CLK uses CBU pin 20/P17, and STB uses CBU pin 17/P28. [#20535534]
GN6932 supports an 8-segment × 16-bit display mode, 8 brightness duty-cycle levels, an RC oscillator at 450 kHz ±5%, and an SOP32 package. [#20535551]
A working display command sequence used LSB-first bytes: 40, then C0 ..., then 8F; decoding it MSB-first made the packet look wrong. [#20536000]
Build 701 added working CHT_Calibrate; the example CHT_Calibrate -2 10 applies −2 °C temperature and +10 %RH humidity offsets. [#20539841]

How do I configure the CHT8305 sensor pins on a Tuya CBU BK7321N/BK7231N USB thermostat in OpenBeken?

Configure CHT8305 as I2C on CBU P22 and P20. Set CHT pin 1, SDA, to CBU pin 4/P22. Set CHT pin 6, SCL, to CBU pin 3/P20. The alert pin was reported as not connected. The thread confirmed the CHT sensor worked after this wiring map. [#20535581]

What is the GN6932 LED display driver and how does it communicate with the CBU module?

GN6932 is the multi-segment LED driver used by this thermostat display. "GN6932 is a display-driver IC that controls multi-segment LED displays, using a serial CLK, STB, and DIN interface with 8-segment × 16-bit output and 8 brightness levels." It receives low-bit-first serial data on CLK rising edges. [#20535551]

How do I start and test the GN6932 display driver in OpenBeken using TMGN commands?

Start the GN6932 driver, then send a TMGN test or print command. Use this 3-step check:

Run startDriver GN6932.
Run GN6932_TestAddressIncreaseMode to light random segments.
Run TMGN_Brightness 7 and TMGN_Print 0 0 123456 to test output. Build 680 already showed changing patterns with the test command. [#20536357]

Why does OpenBeken say “Driver GN6932 is not known in this build” and how do I enable it?

OpenBeken says this when the build excludes the rarely used GN6932/TMGN driver. Newer builds disabled it to reduce flash usage and avoid LittleFS OTA problems. Enable it by compiling with #define ENABLE_DRIVER_TMGN 1 in obk_config.h. A custom build or pull-request build can also include it. [#20979746]

How can I create an autoexec.bat script to show temperature, humidity, and time on the GN6932 LED display?

Create autoexec.bat with GN6932, NTP, brightness, static bits, and a loop. The working example starts GN6932, starts NTP, sets timezone +2:00, prints minutes at offset 7, hours at offset 5, temperature at offset 2, and humidity at offset 0. It also blinks the clock colon by toggling bits 10:0 and 10:1 every 1 second. [#20537716]

What do the numbers mean in the OpenBeken command TMGN_Print 7 2 $minute 1?

7 is the start offset, and 2 is the maximum length. TMGN_Print uses the format TMGN_Print [StartOffset] [MaxLenOr0] [Text]. So TMGN_Print 7 2 $minute 1 prints the two-digit minute value starting at display position 7, with zero padding enabled by the final 1. [#21210176]

How does TMGN_SetBit work for controlling individual LED display segments on TM1637, TM1638, or GN6932 displays?

TMGN_SetBit 9 1 1 means display index 9, bit 1, value on. The first number selects a display byte or digit index, usually within 0–15. The second number selects one of 8 bits, matching 7 segments plus dot. The third number sets that segment off or on, using 0 or 1. [#21205196]

How do I calibrate CHT8305 temperature and humidity readings in OpenBeken with CHT_Calibrate?

Use CHT_Calibrate [temperature offset] [humidity offset] after starting the sensor driver. Build 701 confirmed CHT_Calibrate -2 10 worked. That example subtracts 2 °C from temperature and adds 10 %RH to humidity. Earlier SHT_Calibrate and SHT3X_Calibrate commands failed on CHT8305 because they targeted other drivers. [#20539841]

CHT8305 vs CHT8310: what are the differences and which sensor is used in newer versions of this USB thermostat?

Original units used CHT8305, while newer tested units used CHT8310. The newer board otherwise looked identical in the thread. An older OpenBeken build with GN6932 support lacked newer CHT8310 support, so readings became incorrect. The reported GUI value reached −265 while the LED showed a divided-by-10 temperature figure. [#20980349]

How can I set a static IP address for an OpenBeken device while it is still in AP mode?

Set the static IP from the OpenBeken configuration page while the device runs in AP mode. Choose an address that is unique on your target network. This solves the case where you can join Wi-Fi but cannot access the router page to discover the DHCP address. [#20629101]

What is OpenBeken and why is it used instead of the original Tuya firmware on BK7231N/CBU devices?

OpenBeken is alternative firmware for BK7231N/CBU devices that gives local control, scripting, sensor drivers, and display drivers. In this thermostat, users replaced Tuya firmware to read CHT8305 or CHT8310 data, drive GN6932 LEDs, run NTP time, and restore a working clock-temperature-humidity display without the Tuya cloud. [#20537716]

What is PulseView/Sigrok and how can it help decode DIN, CLK, and STB signals from a GN6932 display?

PulseView/Sigrok captures logic-analyzer traces from GN6932 DIN, CLK, and STB lines. "PulseView/Sigrok is a logic-analysis toolchain that records and decodes digital bus signals, letting users inspect byte order, chip-select timing, and serial display commands." In this case, it revealed LSB-first data and the sequence 40, C0 ..., 8F. [#20536000]

How can I restore the original 2 MB firmware backup to a Tuya CBU device after flashing OpenBeken?

Restore the original 2 MB backup by renaming it for the flasher and placing it in the firmware directory. One user renamed the backup to OpenBK7231N_QIO_1.15.xxx, flashed it, and confirmed the device returned to its original state. This gives a recovery path after OpenBeken testing. [#20535581]

What ESPHome configuration could be used for a BK7231N thermostat with CHT8305 or CHT8310 sensor and GN6932 LED display?

The thread did not provide a working ESPHome configuration for this thermostat. It only requested one in December 2024. The tested path used OpenBeken, a custom build with GN6932 enabled, CHT sensor support, and TMGN scripts. For ESPHome, the missing piece is GN6932 display support equivalent to OpenBeken TMGN commands. [#21350125]

Why might a GN6932 display show humidity and temperature in the wrong positions, and how can channel mapping or TMGN_Map fix it?

The display can show values in wrong positions when channel order or digit mapping does not match the physical grid. One user had to set CHT SDA channels as 1:0 because temperature appeared on the humidity line. For TM1637 mapping issues, the maintainer advised using TMGN_Map instead of TMGN_SetBit. [#20980349]

AI summary based on the discussion. May contain errors.