Making a DIY, "Poor Man's" LN882H development board with 7 segment display out of scrap

p.kaczmarek2 2586 2

TL;DR

A scrap-based LN882H “poor man’s” development board was built from an old satellite tuner to test OpenBeken on the new Lighting Semi platform.
The tuner’s RF, HDMI, and old MCU were removed, then the LN882H module was wired to 3.3V, the HD2015 display controller, IR receiver, extra LED, and header pins.
OBK’s unified "TMGN" driver handled the HD2015 7-segment display, and the board routes out 5V, GND, 3.3V, A0, TX, RX, A1, B9, B3, BOOT, and LED.
A quick test showed the display worked well, and the finished board can drive sensors, relays, potentiometers, and Home Assistant via OBK channels.
The metal cover was replaced with a printed case because it could reduce WiFi range and would be hard to cut.

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Post #1
21137975 30 Jun 2024 16:10

OpenBeken has been recently ported to LN882H platform, and I have received few such WiFi modules from our readers, so it was a good time to think about some kind of "dev board" for this new Lighting Semi platform. The modules I received were unfortunatelly not in TYWE3S/ESP12 format, so I was not able to just place them on NodeMCU, that's why I decided to take a slightly different path. And that path was.... an old sat tuner "hack"!

A typical LN882H module looks somewhat like this:

It requires only 3.3V to work, but for ease of development purposes, some extra peripherals like buttons can be also useful.
That's why I decided to use old sat tuner, the one that I have already described in the past, see related topics:
Running the HD2015 display/button controller after reverse engineering, comparison with TM1650
Salae 24MHz logic analyzer for 10$ - analysis of an unknown LED display protocol

My first step was to remove the not needed parts - I have removed RF and HDMI circuits. SCART will be also removed soon:

I have also removed the old MCU.
Then I checked if the board is still working. Of course, 3.3V is still present. This is good, because 3.3V willbe needed for WiFi module.

Cutting board is messy and may introduce some shorts, so extra caution is needed. I have also cleaned the board after desoldering.

Finally, it was the time for some soldering. This step requires some patience. You also must be extra careful to avoid misconnecting the wires.

In my case, I decided to connect GND and 3.3V to the pads of old 1.8V LDO regulator, which I removed earlier. The 3.3V on this board comes from a step down converter, and step down is fed by 5V from main-powered flyback power supply.
So, soldering time:

Using wire colors can help to remember their roles, white is 3.3V, black is ground.
Then I soldered wires to HD2015 7-segment LED display controller, which is already supported by OpenBeken:

A quick test (after enabling necessary driver in OBK online build) has shown that it indeed works quite well:

OBK provides an united "TMGN" driver for such displays, that can draw numbers and some letters:

Display works, so it's time for the next part.
I have decided to also connect the IR receiver and extra LED, which is not controlled by HD2015:

Finally, I have routed the remaining pins out, to the female goldpin header:

The last thing was to put everything together in the case. I couldn't use metal cover, it could have reduced the WiFi range. Futhermore it would be hard to cut that. That's why I have printed a replacement:

Of course, I have written down the GPIO of my new "dev board":
Code: text Expand Select all Copy to clipboard
5V 5V GND GND 3.3V 3.3V A0 TX RX A1 B9 B3 BOOT LED GND GND

As you can see, all necessary flashing signals are routed out, but still, they should not be required. OTA works good on OpenLN882H. I have also routed out power (both 3.3V and 5V) and ground wires, and some of the GPIO.

I have already made some experiments with my new "dev board" and it works very well. Now I can easily test OpenLN882H, connect sensors like DHT11, BME280, shift registers, relays, potentiometers and much more. This is certainly more handy than just a bare TYWE2S-form module with no peripherals at all... and of course - it's possible to easily pair it with Home Assistant, thanks to OBK channels system.

Soon I may try to make some sample projects on that. Do you have any ideas what should I make? This display could be very useful...

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#2 21138995 01 Jul 2024 12:05

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Post #2
21138995 01 Jul 2024 12:05

How happy I am to get such cool ideas😀😀😀😀😀😀😀
#3 21139016 01 Jul 2024 12:21

p.kaczmarek2 p.kaczmarek2

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Post #3
21139016 01 Jul 2024 12:21

You can also do the same with an Arduino, for example. You take an old piece of hardware, check how it works, and often it's not only the power supply that comes in handy, but also the display, buttons or there IR receiver, etc.
Here I did a similar idea but just on an Arduino:
7 segment tuner display, running from Arduino, sliding register .

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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Making a DIY, "Poor Man's" LN882H development board with 7 segment display out of scrap

FAQ

TL;DR: With 3.3 V power and “Display works” as the key checkpoint, this DIY build turns a scrap sat tuner into an LN882H OpenBeken dev board with a 7-segment display, IR receiver, LED, and exposed headers. It suits tinkerers who need a reusable LN882H test platform without a standard NodeMCU-style footprint. [#21137975]

Why it matters: It shows how to convert discarded consumer hardware into a practical WiFi development board with power, display, and front-panel peripherals already built in.

Option	Fit for LN882H module	Built-in peripherals	Main limitation
NodeMCU-style board	Poor for this module	Usually none for this use	The received LN882H modules were not in TYWE3S/ESP12 format
Recycled sat tuner PCB	Good	7-segment display, IR receiver, LED, power supply	Requires desoldering, cutting, and careful rewiring
Arduino-based reuse approach	Possible alternative	Can reuse old display hardware	Different approach than OpenLN882H on LN882H

Key insight: The reused tuner PCB already provides regulated power and front-panel hardware, so the LN882H module becomes far more useful than a bare module. Exposing BOOT, TX, RX, 3.3 V, 5 V, and GPIO also keeps both OTA and manual flashing practical.

Quick Facts

The LN882H module in this build needs 3.3 V power, and the recycled tuner board still had 3.3 V available after the original MCU, RF section, and HDMI circuitry were removed. [#21137975]
Power routing used the pads of a removed 1.8 V LDO: 3.3 V came from a step-down converter, and that converter was fed by 5 V from the board’s mains flyback supply. [#21137975]
The breakout list exposes 16 header positions: 2× 5 V, 2× 3.3 V, 4× GND, A0, TX, RX, A1, B9, B3, BOOT, and LED. That makes flashing and sensor prototyping much easier. [#21137975]
OpenBeken already supported the HD2015 controller used here, and the unified TMGN driver could draw numbers plus some letters on the tuner’s 7-segment display. [#21137975]
The metal cover was replaced with a 3D-printed one because metal could reduce WiFi range and would be harder to cut cleanly. [#21137975]

How do you turn a scrap sat tuner into a DIY LN882H development board with a 7-segment display?

You remove the old tuner parts, power the LN882H from the board’s existing 3.3 V rail, and wire the display controller to supported OpenBeken pins. 1. Desolder the old MCU and unwanted RF and HDMI circuits. 2. Verify 3.3 V is still present, then solder GND and 3.3 V to the LN882H module. 3. Wire the HD2015 display controller, then route TX, RX, BOOT, power, and GPIO to female headers. [#21137975]

Why was an old sat tuner used instead of placing the LN882H module on a NodeMCU-style board?

The old sat tuner was used because the received LN882H modules were not in TYWE3S/ESP12 format, so they could not be dropped onto a NodeMCU-style board. The tuner PCB also already offered useful extras: a 3.3 V supply, a 7-segment display, an IR receiver, and front-panel hardware. That made it a more practical test platform than a bare module. [#21137975]

What is the LN882H platform, and why is it useful for OpenBeken development?

“LN882H” is a WiFi module platform that runs OpenBeken firmware, requires 3.3 V power, and becomes especially useful when paired with exposed GPIO and onboard peripherals for testing. In this thread, it mattered because OpenBeken had recently been ported to LN882H, and the new board gave the author an easy way to test sensors, relays, shift registers, and Home Assistant integration. [#21137975]

What is the HD2015 7-segment LED display controller, and how does it work with OpenBeken?

“HD2015” is a 7-segment LED display controller that drives a segmented front-panel display, and in this project it works because OpenBeken already supports it through an existing display driver. The author soldered wires from the LN882H board to the tuner’s HD2015 pins, enabled the needed driver in the OBK online build, and quickly confirmed the display was working. [#21137975]

Which parts of the sat tuner board need to be removed before wiring in an LN882H module?

The author removed the old MCU first, then removed the RF and HDMI circuits, and planned to remove SCART later. That cleared space and reduced unused circuitry while keeping the board’s power system alive. The post also warns that cutting the board is messy, so cleanup after desoldering matters before any rewiring starts. [#21137975]

Where should 3.3V and GND be connected on a recycled tuner PCB when powering an LN882H module?

They should be connected to the pads of the old 1.8 V LDO regulator that was removed earlier. In this build, those pads provided a convenient place to pick up GND and the board’s 3.3 V rail. The 3.3 V came from a step-down converter, and that converter itself was fed by 5 V from the mains flyback supply. [#21137975]

How do you connect and test an HD2015 display controller on OpenBeken using the OBK online build?

You wire the LN882H module to the HD2015 controller pins, enable the required display driver in the OBK online build, and run a quick display test. The author did exactly that and confirmed the display worked well. A useful checkpoint was that OpenBeken could already draw numbers and some letters once the driver was enabled. [#21137975]

What is the OpenBeken TMGN driver, and which types of segmented displays does it support?

“TMGN” is a unified OpenBeken display driver that handles segmented LED displays and can draw numbers plus some letters on supported modules. In this thread, it was used with the HD2015-based 7-segment display from the tuner front panel. The post does not list every supported controller, but it explicitly says TMGN works for “such displays” and was enough to make this hardware usable. [#21137975]

How can you route LN882H GPIO, TX, RX, BOOT, 3.3V, and 5V to female headers for easier flashing and prototyping?

You solder the remaining LN882H signals to a female goldpin header so the board exposes power, serial lines, boot control, and spare GPIO in one place. The posted pin list contains 16 positions, including 2× 5 V, 2× 3.3 V, 4× GND, TX, RX, BOOT, LED, A0, A1, B9, and B3. That layout makes manual flashing and sensor hookup much easier. [#21137975]

What precautions help prevent shorts or damage when cutting and desoldering an old tuner motherboard for reuse?

Clean the board after desoldering, inspect for metal debris, and verify power rails before connecting the new module. The author warns that cutting is messy and may introduce shorts, so extra caution is needed. Wire colors also help prevent mistakes: white was used for 3.3 V, and black for GND in this build. [#21137975]

How does HD2015 compare with TM1650 for driving a 7-segment display in a DIY electronics project?

In this thread, the practical comparison is simple: HD2015 was the controller already present on the tuner board, and OpenBeken already supported it, so it was the fastest path. The post references earlier reverse-engineering work and a comparison with TM1650, but it does not provide electrical or protocol differences here. The build choice was driven by existing hardware and working OpenBeken support. [#21137975]

What are the best ways to reuse the IR receiver, extra LED, and front-panel buttons from old set-top box hardware?

The best approach is to keep the tuner’s working front-panel parts and wire them into the new controller as separate test peripherals. In this build, the author explicitly connected the IR receiver and an extra LED that was not controlled by HD2015. He also notes that, in old hardware, not only the power supply but also the display, buttons, and IR receiver often become useful again. [#21139016]

Why replace the metal cover with a 3D-printed one when building a WiFi-enabled LN882H dev board?

The metal cover was replaced because it could reduce WiFi range and would be difficult to cut cleanly. A 3D-printed replacement solved both problems while still letting the modified board fit back into the case. That choice matters more on a WiFi platform like LN882H than on a purely wired test board. [#21137975]

What sample projects can I build with an LN882H dev board that has a 7-segment display, IR receiver, and exposed GPIO pins?

You can use it to test sensors, control outputs, and build small display-based Home Assistant devices. The author specifically lists DHT11, BME280, shift registers, relays, and potentiometers as successful or planned experiments. A practical edge case is display space: the thread proves numbers and some letters, not full text, so compact status readouts fit better than long messages. [#21137975]

How does OTA flashing on OpenLN882H compare with using the routed BOOT, TX, and RX pins for manual flashing?

OTA is the easier day-to-day method here, while routed BOOT, TX, and RX remain a reliable fallback for first setup or recovery. The author says OTA works well on OpenLN882H and also routed out all necessary flashing signals, even though they should not usually be required. That gives the board both convenience and a manual rescue path. [#21137975]