I2C Sensor Control Example

Description

These examples showcases the usage of the nPZero driver to control a sensor connected via the I2C interface. It demonstrates the initialization, configuration, and data exchange procedures required for sensor interaction using the nPZero driver. Sensor in use here is the AMS AS6212.

Code Example Peripheral Mode 1

Code snippet illustrating the usage of the Peripheral Mode 1 for I2C sensor control: This code will set the sensor peripheral to Low Power Switch #2. The Low Power Switch will then be passed as parameter to every function call that has to do with a specific sensor, so it is clear which sensor register should be changed.

• The example will firstly setup the configuration registers for Peripheral Mode 1. This is done in SYSCFG1, CFGP2, MODP2, PERP2.
• Next up we need to configure the communication for Peripheral Mode 1. In this example we will use I2C between sensor and nPZero and so we use ADDRP2 to define I2C Slave Address and set I2C protocol.
• Set NCMDP to number of I2C commands to use for initialize sensor.
• After this we write the I2C initialization commands to SRAM.
• Then define the register that shall be read on wakeup. In this case it is the TVAL register in the AS6212.
• Set the Over and Under threshold registers in the nPZero by setting THROVP2 and THRUNP2.
• Lastly set the TCFGP2 for configuration of the TWTP2 register and also set TWTP2 register to define the wait time between power-on/initialization and initialization.

  void example_peripheral_modes_config_i2c_PM1(np0_device_s device, np0_peripheral_s sensor)
  {
      uint8_t sram_reg = REG_SRAM_START;
      sensor.periph = PSW_LP2;
  
      np0_read_SYSCFG1(&device.syscfg1);
      switch (sensor.periph)
      {
          case PSW_LP1:
              device.syscfg1.wup1 = ENABLED;
              break;
  
          case PSW_LP2:
              device.syscfg1.wup2 = ENABLED;
              break;
  
          case PSW_LP3:
              device.syscfg1.wup3 = ENABLED;
              break;
  
          case PSW_LP4:
              device.syscfg1.wup4 = ENABLED;
              break;
      }
      np0_write_SYSCFG1(device.syscfg1);
  
      sensor.cfgp.pwmod = PWMOD_PERIODIC;
      sensor.cfgp.tmod = TMOD_PERIODIC_INIT_CMP_THRESHOLD;
      sensor.cfgp.pswmod = PSWMOD_POWER_SW;
      np0_write_CFGP(sensor.periph, sensor.cfgp);
  
      sensor.modp.cmod = CMOD_CMP_OUTSIDE_THRESHOLD_MODE;
      sensor.modp.dtype = DTYPE_INT16;
      sensor.modp.seqrw = ENABLE_MULTIBYTE_TRANSFER;
      sensor.modp.wunak = ENABLED;
      sensor.modp.swprreg = BIG_ENDIAN;
      np0_write_MODP(sensor.periph, sensor.modp);
  
      // Wakeup peripheral every 30 seconds with 10Hz clock
      sensor.perp.perp_l = 0x2C;
      sensor.perp.perp_h = 0x01;
      np0_write_PERP(sensor.periph, sensor.perp);
  
      sensor.ncmdp.ncmdp = 2; //# of I2C commands to be sent from SRAM
      np0_write_NCMDP(sensor.periph, sensor.ncmdp);
  
      sensor.addrp.addrp = AS6212;
      sensor.addrp.spi_en = I2C;
      np0_write_ADDRP(sensor.periph, sensor.addrp);
  
  /*================INIT CMDs======================*/
      device.sram.value = 0x01; //Config register (Base register when multi-byte transfer enabled)
      np0_write_SRAM(sram_reg, device.sram);
      sram_reg += SRAM_REG_SIZE;
  
      device.sram.value = 0x02; //Config register++ (base register +1 since multi-byte is enabled)
      np0_write_SRAM(sram_reg, device.sram);
      sram_reg += SRAM_REG_SIZE;
      
      device.sram.value = 0xC5; //MSB first
      np0_write_SRAM(sram_reg, device.sram);
      sram_reg += SRAM_REG_SIZE;
  
      device.sram.value = 0x00;
      np0_write_SRAM(sram_reg, device.sram);
      sram_reg += SRAM_REG_SIZE;
  /*================INIT CMDs END====================*/
  
      //AS6212 TVAL register
      sensor.rregp.rregp = 0x00;
      np0_write_RREGP(sensor.periph, sensor.rregp);
  
      //0x900 = 18 degrees C
      sensor.thrunp.thrunp_l = 0x00;
      sensor.thrunp.thrunp_h = 0x09;
      np0_write_THRUNP(sensor.periph, sensor.thrunp);
  
      //0xC80 = 25 degrees C
      sensor.throvp.throvp_l = 0x80;
      sensor.throvp.throvp_h = 0x0C;
      np0_write_THROVP(sensor.periph, sensor.throvp);
  
      sensor.twtp.twtp = 0x0C; /* 12 (0x0C) * 4096 = 50k clock cycles = 125ms (400kHz)
*                                 12 (0x0C) * 256 = 3k clock cycles = 7.5ms*/
      np0_write_TWTP(sensor.periph, sensor.twtp);
  
      sensor.tcfgp.twt_en = ENABLED;
      sensor.tcfgp.tinit_en = ENABLED;
      sensor.tcfgp.tinit_ext = ENABLED;
      sensor.tcfgp.i2cret = 3;
      np0_write_TCFGP(sensor.periph, sensor.tcfgp);
  
  }

Note

• Modify the code example according to your sensor's specifications and communication protocol.
• Refer to the nPZero driver function documentation for specific function usage.