I am new to Arduino, so please excuse my naivety.
I am in the process of deploying a Home Assistant-based home automation system. Based on various posts and suggestions, I decided to use ESP-8266 based Sonoff S20 WiFi outlets running custom firmware, specifically the KmanSonoff firmware. I read numerous sites and believe that I followed instructions properly, but I cannot flash the device. The error message I am getting is:
Build options changed, rebuilding all
Archiving built core (caching) in: C:\Users\Gerry\AppData\Local\Temp\arduino_cache_220198\core\core_esp8266_esp8266_generic_CpuFrequency_80,FlashFreq_40,FlashMode_dio,UploadSpeed_115200,FlashSize_512K64,ResetMethod_ck,Debug_Disabled,DebugLevel_None_____1107ea9c19db07b2b555edee88bff85e.a
Sketch uses 254427 bytes (58%) of program storage space. Maximum is 434160 bytes.
Global variables use 34824 bytes (42%) of dynamic memory, leaving 47096 bytes for local variables. Maximum is 81920 bytes.
warning: espcomm_sync failed
error: espcomm_open failed
error: espcomm_upload_mem failed
error: espcomm_upload_mem failed
Let me walk you through what I have done and hopefully you can spot my mistake.
Step 1: I purchased a USB-to-serial device, the Sparkfun Serial Basic Breakout - CH340G. I then built a cable to connect the breakout device to the Sonoff S20, see image below.
Step 2: I tested the above by shorting the TX and RX pins and typing into a terminal window. This worked as expected.
Step 3: I soldered a header into the switch. This is a S20_US V1.3 and with this version, the PCB cannot be readily removed from the housing (I suspect one would have to desolder the AC connections to to this). The soldering job is not pretty, but I looked at each joint with my loupe and all appear to be okay. Note: I only had a five pin header floating around - the pin furthest from the button is cut-off.
Step 4: I plugged the Sonoff S20 into the programmer and plugged that into the computer. I observed the green LED flashing, which suggests that power/ground are correctly wired. I then unplugged it, held down the button, and plugged it back into the computer. I clicked Tools->Get Bard info and saw the following:
BN: Unknown board
VID: 1A86
PID: 7523
SN: Upload any sketch to obtain it
To me, this suggests that the devices are communicating. I also tried the Serial Monitor, but there was no response when I entered AT.
Step 5: I then confirmed the Arduino settings, see below, and clicked upload. The error messages were are shown above.
At this point, I am stuck. Please suggest what I might try next. Thank you.