FAQ
TL;DR: CB3S-based TYWRA-RF modules pull a peak 80 mA during Wi-Fi TX (Tuya CB3S datasheet). “After flash, choose Read only OBK config” [Elektroda, fitor, post #21325677] Follow the 3.3 V UART-flash → OBK-config → RF-learn steps to keep both Wi-Fi and 433 MHz control.
Why it matters: One wrong jumper or 5 V feed fries the AMS1117 regulator and kills the relay.
Quick Facts
• Supply voltage: 3.3 V UART, 5 V micro-USB for load side [Elektroda, fitor, post #21324638]
• Peak Wi-Fi current: 80 mA, average 46 mA (CB3S datasheet)
• RF carrier: 433.92 MHz, pulse width ≈ 345 µs [Elektroda, Dump, post #21324150]
• Flashing time with BK7231 GUI: ≤ 90 s typical [Elektroda, GastonL, post #21325559]
• AMS1117 regulator max dissipation 1 W @ 25 °C (AMS1117 datasheet)
Does flashing OpenBK7231C remove the 433 MHz RF learning feature?
No. Keep the Tuya RF parameters (remote_add_dp, remote_list_dp, rf_width, remote_io) in the JSON. When they stay intact, the long-press on P6 still enters RF-learn mode
[Elektroda, fitor, post #21324150]
How do I teach the relay a new RF remote after flashing?
- Hold the on-board button (P6) for >5 s until the LED blinks fast.
- Press the desired RF key twice within 10 s.
- LED turns steady—code stored in flash [Elektroda, divadiow, post #21308412]
Why can’t I open the web interface even though the module gets an IP?
What UART pins do I need on the CB3S module?
Safe flashing procedure in 3 steps?
- Wire RX–TX, TX–RX, GND; power via USB.
- Start BK7231 Flasher, click ‘Start’.
- Momentarily short GND to pin 1 (RST) to enter boot, then release; flash completes in ≈90 s [Elektroda, GastonL, post #21325559]
What causes the AMS1117 regulator to smoke?
Feeding 5 V to the 3.3 V rail or shorting TX-RX directly to USB 5 V overloads the AMS1117, which can dissipate only 1 W max [AMS1117 datasheet; Elektroda, GastonL, #21325907].
Will swapping TX and RX lines damage the board?
What GPIOs control the relay and LEDs by default?
Typical current draw in deep-sleep?
CB3S deep-sleep current is approx. 20 µA, extending battery lifetimes in sensor designs [Tuya CB3S datasheet].
Edge case: One of four relays lost RF after flashing—why?
A corrupted RF parameter block at offset 0x2023424 disables the 433 MHz ISR. Restore the JSON from a working dump or set ‘remote_select 1’ via UART and reboot
[Elektroda, fitor, post #21324150]
How many RF codes can the module store?
Can I power the CB3S directly from 5 V?
No. Feed 5 V only to the on-board AMS1117 input. The CB3S core must see 3.3 V; exceeding 3.6 V risks permanent damage [AMS1117 datasheet].
Generated by the language model.
Comments
Yes thnx this wil help, but now it is just a wifi controlled relais, how can i learn a new RF remote control? [Read more]
Hi, did anyone solve this problem? Thanx [Read more]
are you sure RF matching must be done through software? I notice the manual only makes mention of the app method, but my experience with the switches I have with RF capability is that a long-push of one... [Read more]
Hi, I have the instructions manual. But xinetic mentioned that the RF transmitter cannot be learned after flash, so far I relay not flash because I want to keep the RF function. I will try to pick up... [Read more]
I flashed the relay successfully, it connects to wifi but cannot connect to the web interface :-( It's there way to reach settings in another way? [Read more]
Hi, does anyone have experience with this problem. The relay has an address assigned to it by the router, but i cannot connect to it after entering the address into the browser. I can change the parameters... [Read more]
Hi, I have the same smart switch. Can you tell me how you flashed it? Did you connect an uart/usb device, and if so, how did you wire it? [Read more]
Hi, standard conection via UART, module CB3S: PIN1 - CEN PIN8 - Vcc PIN9 - GND PIN15 - RX PIN16 - TX { "rl1_lv":"1", "on_off_cnt":"10", "onoff_rst_m":"0", "led1_pin":"9", "onoff_clear_t":"6", "rand_dpid":"42", "net_trig":"4", "netled1_lv":"0", "jv":"100", "onoff_rst_type":"2", "total_bt_pin":"6", "nety_led":"0", "total_stat":"0", "reset_t":"5", "netled1_pin":"8", "remote_add_dp":"49", "remote_list_dp":"50", "net_type":"0", "inch_dp":"44", "rf_width":"345", "module":"CB3S", "ch_cddpid1":"9", "remote_io":"26", "onoff1":"14", "init_conf":"38", "led1_lv":"0", "zero_select":"0", "onoff_type":"0", "series_ctrl":"0", "total_bt_lv":"0", "cyc_dpid":"43", "remote_select":"1", "ch_num":"1", "rl1_pin":"24", "netn_led":"0", "ch_dpid1":"1", "crc":"16" } Device... [Read more]
That's how I connected it, but I did not unsoldier the cb3s. I tried to reset through pin 1 (reset) and pin 3 (cen), but without luck. Do I have to unsoldier the cb3s for that? I measured voltage over... [Read more]
That's weird. If you have a weak 3V3 power supply on the UART, you can use an external stabilizer. But the easiest way is to just connect Rx, Tx and GND and power the relay through its micro USB port.... [Read more]
Your suggestion did help me, but it works differently for me. Steps I did: 1. wire TX, RX and GND 2. connect USB/UART to computer 3. start (windows) BK7231 UART flasher 4. connect switch to USB for... [Read more]
After flash, choose Read only OBK config, then Change OBK settings and here put wifi SSID and password, then Write only OBK config. For wifi is not necesary to tick any flags. [Read more]
That was easy, but I think I fried the AMS 1117 voltage regulator, because the led is on with a fast flicker, there is no WIFI and there is no response from buttons or relay (the AMS started smoking... [Read more]
Swapping Tx and Rx will not destroy the chip. You must have switched the polarity of the power supply. [Read more]
I agree that it's unlikely to destroy the chip with swapping Tx and Rx. But it's also unlikely to swap polarity using a USB cable to power the switch. I found a AMS1117 on a step down converter and tried... [Read more]
Didn't you use a 5V power supply instead of 3V3? [Read more]
I used the uart on 3v and the USB is the regular way to power the switch (which is 5v of course). Apart from Tx and Rx I don't think anything was connected wrong. But we will never be sure [Read more]
Guys, how do I set the device so that after pressing the button, the relay turns off after 1 second? [Read more]
RF support and guide available BK7231 RF receiver driver tutorial - how to use SYN590R or similar to control multiple devices @fitor I see your extraction contains "remote_io":"26" [Read more]