Notes on flashing the ESP8266 wifi module (ESP-01S)

Writing this down for future reference. I used a Sparkfun FTDI breakout board with selectable voltage level set to 3.3v. Pinout

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TXD <-> TX (I suspect wrong labelling)
RXD <-> RX
VCC <-> 3v3
GND <-> GND
        IO0 pulled low
        IO2 pulled high

Keep the reset pin connected to a wire for easy resetting.

Install esptool.py via pip install esptool and then when the ESP8266 is set to flash mode (IO0 low IO2 high) we can then try to connect at 115200 baud.

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esptool.py --port /dev/tty.usbmodem1421 --baud 115200 read_mac

I flashed v2.1.0 of the NON OS SDK which can be obtained here.

Flash details

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boot_v1.7.bin @ 0x0
at\512+512\user1.1024.new.2.bin @ 0x01
esp_init_data_default.bin 0xfc000
blank.bin @ 0xfe000 0x7e000 0xfb000 0xfb000

SPI crystal frequency of 26MHz, speed 40MHz, 8Mbit flash size, QIO flash.

The firmware sets default baudrate to 1152000. This was confusing for me because I’m used to working with serial devices and I just assumed it was 115200 (a more standard baudrate). Use a serial monitor that can connect on that baudrate and then change the default by typing

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AT #for testing
AT+GMR #for testing
AT+UART_DEF=9600,8,1,0,0

Now you can use minicom again but you have to remember to press ctrl M ctrl J to send CRLF like so

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AT^M^J