Coinos Printer

This code can be flashed onto a Xiao Seeed ESP32 C3 to instruct it to connect to a WiFi AP and control a thermal printer.

The code will establish a connection to Coinos and listen for payments that are received into a specified account.

See this video for an overview, the build process is shown at the end: https://www.youtube.com/watch?v=JiGoOJZUrP8

If it has trouble connecting to WiFi, it will go into AP mode and create a network called CoinosPrinter with password 21bitcoin which will allow you to reset its WiFi and Coinos credentials by visiting http://192.168.4.1

When a payment is detected, a receipt will be printed with the amount and time of the transaction.

The printer looks for MQTT messages with these prefixes

pay: - indicates an incoming payment payload to be printed
update: - instructs it to fetch a new firmware from https://coinos.io/api/public/coinos-printer.ino.bin and flash itself
creds: - tells it to use new wifi and coinos credentials
msg: - tells it to print whatever text you send it

The printer will periodically check in with a health update so you can remotely monitor its status in the field.

Install arduino-cli

curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | sh
arduino-cli config init

Edit $HOME/.arduino15/arduino-cli.yaml to add ESP32 package url:

board_manager:
  additional_urls:
    - https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

arduino-cli core update-index
arduino-cli core install esp32:esp32

Install mklittlefs

wget https://github.com/earlephilhower/mklittlefs/releases/download/3.2.0/x86_64-linux-gnu-mklittlefs-975bd0f.tar.gz
tar xf x86_64-linux-gnu-mklittlefs-975bd0f.tar.gz

Install esptool

pip install esptool

Configure your WiFi and Coinos credentials

# edit data/config.txt

Create the LittleFS partition

mklittlefs -c data -p 256 -b 4096 -s 0x20000 littlefs.img

Flashing

arduino-cli compile -b esp32:esp32:esp32c3 --libraries $PWD/libraries --build-property build.partitions=min_spiffs -u -p /dev/ttyACM0
esptool.py --port /dev/ttyACM0 write_flash 0x3D0000 littlefs.img