Electric Imp Device Code for Si7020 Breakout Board

read_Si7020_device

// Define the Sensor Address
const ADDR = 0x80;

// Define register map
const HUMIDITY = "\xE5";
const TEMP_FROM_RH = "\xE0";

// Specify the update rate in seconds
const update_rate = 60;

// Define the i2c periphrial being used
i2c <- hardware.i2c89;

// Configure said periphrial
i2c.configure(CLOCK_SPEED_100_KHZ);
 
// function to read the Si7020 sensor via configured i2c periph
function readSensor() {
  // Read the humidity, sensor uses i2c clock stretching to hold the transaction while it is
  // taking the measurement, this will block the thread for 16.5ms (typical)
  local rh = i2c.read(ADDR,HUMIDITY,2);
  
  // Part of taking a humidity reading is getting the temp, so read that out
  local t = i2c.read(ADDR,TEMP_FROM_RH,2);
  
  // Push this data off to the Agent for processing, avoid dooing much math so that we
  // can go back to sleep...
  agent.send("sample",[rh[0],rh[1],t[0],t[1]]);
  
  // Schedule the next reading
  imp.wakeup(update_rate, readSensor);
}

// start the loop
readSensor();