Add docs to explain the display component (`TTL-WIFI`)

[syssi]

See #45. Mention the pinout of the TTL-WIFI connector: 5V, TX, RX, GND

[user0x01]

Can i flash the wlan interface (V1.7) with the esphome display component,
with a 5V ftdi adapter on den "USB"-Port and GPIO0 on Ground?

[syssi]

I didn't tried it yet because I still need the stock firmware for reverse engineering. In general it should be possible and it would be the good choice because the wifi interface board is equipped with a logic level shifter because the 5V TTL of the STM32 at the Soyosource mainboard.

Please keep in mind: At the moment you cannot control the Soyosource using the display component. You can just retrieve all measurements. The "write all config regidterst" frame isn't implemented yet. But it's no big thing to do it.

[syssi]

Another thought: I never traced the connection between the USB jack, the microcontroller used as a level shifters (this is a guess) and the ESP. It's possible the RX and TX lines aren't connected to GPIO1 and 3 of the ESP. May be another GPIO using software serial is used here. In other words: If flashing using the USB jack doesn't work you should connect the FTDI directly to the ESP. As next step you have to identify the GPIOs "connected" to the USB jack to configure the UART component accordingly.

[syssi]

Feel free to ask for details. I will have a look at the WiFi interface and try to provide some support. In best case I can backup the stock firmware and can give it a try too.

[user0x01]

You're probably right.

I get on grip1+3 only this message AT+INFO=ok
Module Type=0, Software Version=1106
Copyright By www.51byb.com.

The payload pins seem to be different.

[syssi]

I also made some progress. I've attached a logic analyzer to all soldered pins of the ESP8266. It looks like this:

If I power the board (5V) and listen to the traffic at the TX pin of the USB connector I can see periodic requests:

55 02 00 00 00 00 00 00 00 00 00 fd

If I check the logic analyzer there is no traffic at the GPIOs of the ESP8266. If I connect to the WiFi accesspoint now and open the Soyosource app the blue LED of the ESP8266 flickers and I can see requests + responses on GPIO1/GPIO3:

Funny thing: The requests at the USB connector are still different (0x55 0x02 vs. 0x55 0x03). I assume the Nuvoton uC on the back of the PCB isn't a "transparent proxy". It looks like the firmware is slightly "protocol aware".

Long story short: You cannot flash the ESP8266 via the USB connector. You have to use GPIO1 and GPIO3 directly. The 4+1 pin header at the PCB doesn't expose the GPIOs of the ESP. The header is connected to the Nuvoton uC. As soon ESPHome is flashed to the ESP the Nuvoton shouldn't notice the difference and communication using the display protocol should be possible.

[user0x01]

Cool.

I try it.
My Jumperwires holds perfect in the holes off the esp.
Das geht, ohne dass ich was löten muss.

[syssi]

I've added some more details about the WiFi Dongle V1.7 here: https://github.com/syssi/esphome-soyosource-gtn-virtual-meter/tree/main/docs/wifi-dongle

[syssi]

I've added some instructions how to dump the flash content: https://github.com/syssi/esphome-soyosource-gtn-virtual-meter/tree/main/docs/wifi-dongle

I learned: The message Module Type=0, Software Version=1106\nCopyright By www.51byb.com. is transmitted from the Nuvoton uC. If you see this message you have to swap RX/TX to be able to talk to the ESP32 as soon the MS51 is stopped by pulling nRESET down.

[user0x01]

When I use uart in the config, the ESP disappears from router.
I think the Nuvoton is probably the master, the ESP just the wifi interface.

[syssi]

This sounds like the ESP crashs. Could you attach a USB-to-TTL adapter to GPIO1/GPIO3 to monitor the boot process? You should see the reason for not joining the WiFi here.

[syssi]

I didn't find any other connections next to the serial line between the ESP and the Nuvoton MS51 yet. This means the MS51 isn't able to reset/reboot the ESP or control some other import GPIOs. Only the serial line is used for communication/instructions between the microcontrollers.

Let's call the MS51 the "primary" because the LEDs and the button are attached to this microcontroller and this uC decides about the operation mode of the ESP (by sending some AT command to switch the mode).

[syssi]

I don't want to flash my WiFi dongle as long as the following features aren't ready: #51, #52, #53
If restoring the stock firmware doesn't work I'm stuck.