Analysis of original wifi-module to find powersource for ESP8266

[ThinkPadNL]

I am investigating if it is possible to feed the ESP8266 and RS485-TTL-converter from the power that the inverter offers for the original wifi-module, instead of using an external USB-powersupply.

I carefully opened the original Goodwe wifi-module, it resembles a PCB ("190-00069-00") with a Rakwireless RAK41X module (P/N: 151-30028-00). According to a sticker on the module it uses RAK496.

With some Googling i found this interesting page which has pictures and wifi certification stuff about the chip, but also the datasheet of the chip (should the page go offline, i saved a copy of the datsheet here User-manual-2799522.pdf.

What i was interested in, is the voltage that the chip needs to work. It needs 3.3V according to the datasheet. On the PCB we see a TO-252 package, i suspect that this is a voltage regulator (haven't found datasheet yet). Following the traces to the white connector, i found out that power is supplied through pins 1 and 2. When measuring on the Goodwe while it is active, it supplies +5V on pin 1 and the GND is on pin 2.

I will investigate some more on the voltage converter, to find out if the Goodwe would be capable of powering our ESP8266's.

Some additional information: apparently the protocol that the wifi-module uses to talk with the inverter is SPI according to the datasheet. I think it uses pin 3, 4 and 5 for that. It is a bit unclear which pin does what. It looks like pin 4 is MISO but not sure. I will not investigate this further, as we already have working communications over RS485. I am just writing it down here, in case someone else could need it.

To be continued.

[ThinkPadNL]

Measuring power consumption of original Goodwe wifi-module
Applying 5V to pin 1 and connecting GND to pin 2 gives me a working Goodwe wifi-module, while it is lying on my desk. I can connect to the wifi network and browse around in the web interface. I did this so i could determine the power consumption of the original module, which is 96 mA.

Measuring ESP8266 & RS485-TTL-converter power consumption
I also measured the Wemos D1 Mini + RS485-TTL converter and these together use 74 mA.

Connecting it to the Goodwe inverter
As I am now convinced that it does not consume too much power (which could possibly damage the Goodwe?), i just connected the setup to the inverter and can confirm that powering the setup works with my GW3000-NS !!

The orange wire i have connected to the '5V' pin of my Wemos D1 Mini. The blue wire goes to the pin 'G' (ground).

I will monitor this for a few days to see if it works stable. And order myself a male JST-XH connector to replace these wires 😆

[ThinkPadNL]

So far so good! As expected the ESP8266 will lose power when the sun has gone down and the inverter powers off. But this morning it was happily uploading to PVoutput again!
I had contact with the author of the repo about this, he said that the downside is that MQTT values are resetted at midnight by the ESP. With my solution the ESP loses power before midnight, so that might give you incorrect values over MQTT (see also #21).

Conclusion: yes it works, but it depends on your usecase if it is a suitable solution for you.