GCBASIC documentation
I2C Software

Syntax:

  I2CReceive data
  I2CReceive data, ack

Command Availability:

Available on all microcontrollers except 12 bit instruction Microchip PIC microcontrollers (10F, 12F5xx, 16F5xx chips)

Explanation:

The I2CReceive command will send data through the I2C connection. If ack is TRUE, or no value is given for ack, then I2CReceive will send an ack.

If in master mode, I2CReceive will read the data immediately.

If in slave mode, I2CReceive will wait for the master to send the data before reading. When the method I2CReceive is used in Slave mode the global variable I2CMatch will be set to true when the received value is equal to the constant I2C_ADDRESS.

Note:

Earlier versions of GCBASIC provided a separate I2CSlaveDeviceReceive command for slave-mode reception. That name is now a reserved legacy identifier only — the functionality has been folded into I2CReceive itself, conditioned on #define I2C_MODE Slave, exactly as shown in Example 2 below.

Example 1 - Master Mode:

  ' I2C Receive - using the ChipIno board, see here for information. ' This program reads an I2C register and LED is set to on if the value  is over 100.
  ' This program will read from address 83, register 1.

  #chip 16F886, 8
  #config MCLRE_ON

  'I2C settings
  #define I2C_MODE Master
  #define I2C_DATA PORTC.4
  #define I2C_CLOCK PORTC.3

  'Misc settings
  #define LED PORTB.5
  dir LED Out

  'Main loop
  Do
    'Send start
    I2CStart

    'Request value
    I2CSend 83
    I2CSend 1

    'Read value
    I2CReceive ValueIn          ' <<< the I2CReceive instruction

    'Send stop
    I2CStop

    'Turn on LED if received value > 100
    Set LED Off
    If ValueIn > 100 Then Set LED On

    'Delay
    Wait 20 ms

  Loop

Key line: I2CReceive ValueIn — reads one byte from the I2C bus into ValueIn, automatically ACKing since no ack argument was given.

Example 2 - Slave Mode:

See the I2C Overview for the Master mode device to control this Slave mode device.

  ' I2CReceive_Slave.gcb - using a 16F88.
  ' This program receives commands from a GCB Master. This Slave has three LEDs attached.

  ;----- Configuration

  #chip 16F88, 8
  #config MCLR_OFF


  #define I2C_MODE    Slave     ;this is a slave device now
  #define I2C_CLOCK   portb.4    ;SCL on pin 10
  #define I2C_DATA    portb.1    ;SDA on pin 7
  #define I2C_ADDRESS 0x60      ;address of the slave device

  ;----- Variables

  dim addr, reg, value as byte

  ;----- Program
  #define LED0  porta.2          ;pin 1
  #define LED1  porta.3          ;pin 2
  #define LED2  porta.4          ;pin 3

  dir LED0 out                  ;0, 1 and 2 are outputs (LEDs)
  dir LED1 out                  ;0, 1 and 2 are outputs (LEDs)
  dir LED2 out                  ;0, 1 and 2 are outputs (LEDs)

  do
    I2CStart                 ;wait for Start signal
    I2CReceive( addr )         ' <<< the I2CReceive instruction (slave mode)

    if I2CMatch  = true then    ;if it matches, proceed

    I2CReceive(regval, ACK)   ;get the register number
    I2CReceive(value, ACK)    ;and its value
    I2CStop                   ;release the bus from this end

    select case regval        ;now turn proper LED on or off
      case 0:
      if value then
        set LED0 on
      else
        set LED0 off
      end if

      case 1:
      if value then
        set LED1 on
      else
        set LED1 off
      end if

      case 2:
      if value then
        set LED2 on
      else
        set LED2 off
      end if
      case else
           ;other register numbers are ignored
    end select
    else
     I2CStop           ;release bus in any event
    end if

  loop

Key line: I2CReceive( addr ) — in slave mode, this blocks until the master sends the address byte, then sets I2CMatch to true if it equals this device’s own I2C_ADDRESS.

See Also:

Supported in <I2C.H>