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Wifi flashing and UART

So while using the ESP8266 with OpenEVSE is not a new thing, I thought I'd share my recent tweak to my OpenEVSE box.

The clever flolk over at arduinos esp8266 section made esp8266avrisp so you can flash the board over wifi, and I hacked in a simple uart-tcp bridge giving me access to the serial port as well.

Picture attached shows a mains to 5v ac/dc converter the tiny Digistump Oak esp8266 and an arduino uno, all connected without level shifting, as it turns out the esp8266 gpio is 5v tolerant. (IMPORTANT: the esp8266 needs 3.3 supply, but the Oak handles this onboard!).

A 6 pin connector to the ICP port and 2 pin connector to the uart. Works as a charm so far. I will probably add 100ohm series resitors just to be on the safe side. But I was pleasantly surprised to learn about the 5v tolerance after strugling with a TXB0108 and the reset line, but at last no need!

Link to the avrisp code,  and i flashed it from my computer directly to the esp IP address:


avrdude -c arduino -patmega328p -P net: -Uflash:w:../open_evse-temp-r02.hex


Code compiles and uploads in the Arduino IDE. Recommend looking for WeMos D1 mini modules as they are almost as compact as the Oak but a fraction of the cost. Or use a plain esp8266 module and a 3.3v supply directly (but then you need a uart to ttl cable to flash the esp).

No more opening the enclosure to program and fighting with the bluetooth serial link! Good times.

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