I2CSend

Syntax:

	I2CSend data
	I2CSend data, ack

Command Availability:

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

Explanation:

The I2CSend command will send data through the I2C connection. If ack is TRUE, or no value is given for ack, then I2CSend will wait for an Ack from the receiver before continuing. If in master mode, I2CSend will send the data immediately. If in slave mode, I2CSend will wait for the master to request the data before sending.

Example 1:

	' I2CSend - using the ChipIno board, see here for information.
	' This program send commands to a GCB Slave with three LEDs attached.

	#chip 16F886, 8
	#config MCLRE_ON

	'I2C settings
	#define I2C_MODE Master
	#define I2C_DATA PORTC.4
	#define I2C_CLOCK PORTC.3
	#define I2C_BIT_DELAY 20 us
	#define I2C_CLOCK_DELAY 30 us


	#define I2C_ADDRESS 0x60      ;address of the slave device
	;----- Variables

	dim reg as byte

	;----- Program

	do

	  for reg = 0 to 2            ;three LEDs to control
		I2CStart                  ;take control of the bus
		I2CSend I2C_ADDRESS       ;address the device
		if I2CSendState = ACK then
		  I2CSend reg               ;address the particular register
		  I2CSend ON                ;command to turn on LED
		end if
		I2CStop                   ;relinquish the bus
		wait  100 ms
	  next reg
	  wait 1 S                  ;pause to show results

	  for reg = 0 to 2            ;similarly, turn them off
		I2CStart                  ;take control of the bus
		I2CSend I2C_ADDRESS       ;address the device
		if I2CSendState = ACK then
		  I2CSend reg               ;address the particular register
		  I2CSend OFF               ;command to turn off LED
		end if
		I2CStop                   ;relinquish the bus
		wait  100 ms
	  next reg
	  wait 1 S                  ;pause to show results

	loop

Example 2:

	'This program will act as an I2C analog to digital converter
	'When data is requested from address 83, registers 0 through
	'3, it will return the value of AN0 through AN3.

	'Chip model
	#chip 16F88, 8

	'I2C settings
	#define I2C_MODE Slave
	#define I2C_CLOCK PORTB.0
	#define I2C_DATA PORTB.1

	#define I2C_DISABLE_INTERRUPTS ON

	'Main loop
	Do
		'Wait for start condition
		I2CStart

		'Get address
		I2CReceive Address
		If Address = 83 Then
			'If address was this device's address, respond
			I2CReceive Register

			OutValue = ReadAD(Register)
			I2CSend OutValue
		End If

		I2CStop

		Wait 5 ms
	Loop

Specific control of I2CSend

The I2CSend method can be controller with command(s) the change the behaviour of method.  The behaviour can be changed as a Prefix or Suffix therefore the start or end of the method.

The two macros ( defined constants) are I2CPreSendMacro and I2CPostSendMacro.  The macros must be a single line, with colon delimiters are permitted.

Examples

The following defined macros change the start and end behaviour.

		#define I2CPreSendMacro if LabI2CState <> True then exit Sub  'I2CPreSendMacro to ensure GLCD operations only operate within specfic lab
		#define I2CPostSendMacro if LabI2CState = True then MSSP =1   'I2CPostSendMacro to ensure GLCD operations only operate within specfic lab setting a specific variable.

The following defined macro changes- the start behaviour to call an alternative I2CSend method.

		#define I2CPreSendMacro     myI2CSend: exit sub


        sub myI2CSend
            // your i2C handler
        end sub

The following defined macros changes- the start behaviour to call an alternative I2CSend method, then jump to the I2CPostSendMacroLabel which is at the end of I2CSend method. 

		#define I2CPreSendMacro         myI2CSend: goto I2CPostSendMacroLabel
        #define I2CPostSendMacro        NOP

        sub myI2CSend
            // your i2C handler
        end sub

This will generate the following ASM.  The I2CPreSendMacro calls the MYI2CSEND() methhod, then BRAnches to the label I2CPOSTSENDMACROLABEL as the end of the method. 

		;Source: i2c.h (339)
		I2CSEND
		;I2CPreSendMacro
			rcall	MYI2CSEND
			bra	I2CPOSTSENDMACROLABEL
		;I2C_CLOCK_LOW                 'begin with SCL=0
			bcf	TRISC,3,ACCESS
			bcf	LATC,3,ACCESS
		...
		lots of ASM
		...
		;wait I2C_BIT_DELAY            'wait the usual bit length
			nop
			nop
		I2CPOSTSENDMACROLABEL
		;I2CPostSendMacro
			nop
			return

Supported in <I2C.H>

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