I2C communication between Pi 4 & ESP32

[bgoodwine]

Establishing I2C connection

Arduino Wire library Arduino twi library that Wire uses I2C Python SMBUS Doc

LED blinking tutorial

Connect GPIO2 on Pi 4 to 22 on ESP32 (SDA) Connect GPIO3 on Pi 4 to 21 on ESP32 (SDL)

I2C tools:

• ls /dev/*i2c* to show which I2C port is being used on Pi 4 (current: /dev/i2c-1)
• i2cdetect -y 1 to list all devices connected on I2C port/bus 1 (i.e. SDA = GPIO2, SCL = GPIO3)

[bgoodwine]

Protocol

• Checkins - sensor failure detected if IMU data does not match
• Alert tumbling
• Receive SDR transmission messages
• Receive shutdown/restart sensor commands
• Any communications about MPPT?

[bgoodwine]

Protocol Draft 1

Pi initial requests:

• 0: = request for general checkin
• 1:[IMU data] = IMU data that the ESP32 should either confirm or alert mismatching data
• 2:message = transmit message via SDR
• 3:sensor_id = restart sensor corresponding to sensor_id
• 4:sensor_id = shutdown sensor corresponding to sensor_id
• 0:2 = start relay of available SDR message (sent after receiving 0:2 from ESP32)
• 0:3 = start relay of solar panel efficiency report (sent after receiving 0:3 from ESP32)

ESP32 response to general checkin:

• 0:0 = not tumbling
• 0:1 = tumbling alert
• 0:2:[num_bytes] = message from SDR waiting to be relayed
• 0:3:[num_bytes] = solar panel efficiency report available for relay

ESP32 response to IMU data:

• 1:0 = IMU data is good
• 1:1 = IMU data does not match
• 1:report:[solar panel report] = solar panel efficiency report
• 2:num_bytes = number of bytes in message received from the SDR, which the ESP32 will next relay to the Pi
• 2:[message] = message relayed to Pi, will only be num_bytes long

ESP32 data relay:

• 2:[message] - SDR message to relay, repeat until num_bytes has been sent (-2 for each sent message)
• 3:[report] - solar panel efficiency report to relay, repeat until num_bytes has been sent (-2 for each sent message)