How to flash Tasmota on an ESP8285-based Elivco Tuya door sensor

[spupetic]

Update: The solution is to put a solder blob or a little wire to the place of the missing R2, then you can back up the original firmware and flash it with Tasmota. Before you do that, please sniff the communication between JS2303 and the ESP8285 chip while having the Tuya firmware on the device.

Original question:

Hi everyone! I would like to ask for some advice about flashing a generic Elivco Tuya door sensor with Tasmota, as I have tried to do it via serial and also with tuya-convert, but I could not do it. The pins are exposed and labeled, I have connected it properly, but it seems like the RX on the board is not active somehow, the TX line sends data (Tuya logs when not in flash mode), but somewhy I cannot get it to display correctly (tried several baud rates). esptool times out, I cannot read the flash, the web flasher does not work either. I have tried to ground GPIO0 to enter flash mode, that seems successful, but from there, I cannot get it to flash.

I have also tried powering the device externally, that did not help.

The label on the board says: FL-S157-V1.3

[barbudor]

Your device doesn't seems to have a Tuya MCU which is generally the cause of such trouble as it drives the RX pin of the ESP.
If you are sure that there's nothing connected to the ESP's RX pins, the other pain point on battery operated device is a circuit that resets the ESP to force a low power mode. Check what could be connected to the RST or the CH_EN pins

[sfromis]

You could also try keeping the sensor active while working with it, giving it no rest, as a door sensor may indeed power off the ESP8266 shortly after last detected movement.

[spupetic]

Thank you for the tips, I have tried again, this time, moving the magnet around, and it started flashing, but only got to the point where it erased the flash, so now the original firmware is gone. It seems like that the hall sensor powers on the ESP, but with the original firmware, it went along and created an AP without the circuit shutting it down. What can I do, to keep it powered on? There are some other pads exposed, I suspect, that there should be a mode what allows flashing.

[sfromis]

Speculation: Maybe the 6-pin chip near the center hole is some sort of timer, it does seem to have connections to the ESP8285 chip, which might be able to control the timing. In that case, it might be feasible to supply power around that chip. Beware that, in that case, you might have to work out how to manage the timing from Tasmota.

[spupetic]

Thanks, I will check it out.

[CoderMal]

I have the same unit. I was able to flash it using Tasmotizer but cannot figure out how to control the JC2303. Does anyone have a datasheet for the JC2303? Searching comes up empty. It is used to control the CHIP_EN through GPIO4 and is tied to both GPIO5 (hall sensor) and GPIO12 (button on bottom) for wakeup.

JC2303 Pinout is:
1 - GPIO12
2 - GND
3 - GPIO5
4 - CHIP_EN
5 - VCC
6 - GPIO4

[spupetic]

How did you flash it with Tasmotizer?

[CoderMal]

If you already configured the device via a Tuya app the device will quickly go to sleep before you get a chance to flash it. You will need to reset the device by holding the reset button on the bottom until the led blinks quickly.

Before flashing. Please check how the ESP controls the JC2303 with an oscilloscope or logic analyser. I cannot find the datasheet and without knowing the communications, you will not be able to put the ESP into power-down state, thus killing batteries in a few days.

Please post your findings.

[spupetic]

Unfortunately, I have already erased it while trying to flash, it only went through that point via esptool, and cannot even started with Tasmota's web flasher, my unit is now bricked. I don't have the Tuya firmware anymore, but the chip still wakes up the ESP when moving the magnet around.

[CoderMal]

Have you tried to putting CHIP_EN to VCC (bypassing the JS2303)? You can do this with a little wire or solder blob on the missing R2 by the CHIP_EN pin.

Tasmotizer running on windows has always been my go-to. https://github.com/tasmota/tasmotizer

[spupetic]

Unfortunately, I did not have time to check it. I have tried to look up the JS2303 online too, had no luck with it. But... Do we need it? Cannot we just put the ESP into deep sleep after it sent the MQTT message? The ESP wakes up to a door event without firmware on it, so the controls may not require other communication, like the JS2303 resets the ESP, it wakes up, sends the message, and the software turns it to deep sleep.

[spupetic]

Have you tried to putting CHIP_EN to VCC (bypassing the JS2303)? You can do this with a little wire or solder blob on the missing R2 by the CHIP_EN pin.

Tasmotizer running on windows has always been my go-to. https://github.com/tasmota/tasmotizer

Soldering onto the missing R2 worked, thank you. Now the device runs Tasmota. Have you been able to figure out what can be done about the JS2303?

[CoderMal]

Glad it worked for you. I think the JS2303 on my board is damaged. I order another unit so when it arrives, I will confirm.

[spupetic]

Glad it worked for you. I think the JS2303 on my board is damaged. I order another unit so when it arrives, I will confirm.

I see. What could have happened to it?

[burbon-pl]

Hello,

Did anyone succeed to make this thing running? I've managed to upload tasmota (R2 shorted), found out that LED is probably on GPIO13, TX at GPIO1,RX GPIO3. Hall sensor imho should be on GPIO4, as there is the JS2303 connected.
JS2303 wakes this thing up for so short time I don't think it's possible to connect to wifi and send anything. Anyone tried bypassing JS2303 (connecting hall sensor directly to ESP8285, and shortening R2)?