PIC32MX: I2C Communication between PIC32s - Revision history

NickMarchuk at 20:17, 1 March 2010

2010-03-01T20:17:34Z

Thomas Peterson: /* Master Code */

2010-02-24T16:10:34Z

Master Code

JamesRein: /* Slave Code */

2010-02-16T04:45:55Z

Slave Code

JamesRein: /* Slave Code */

2010-02-16T04:44:53Z

Slave Code

JamesRein: /* Overview */

2010-02-16T04:39:26Z

Overview

JamesRein: /* Code */

2010-02-16T04:18:45Z

Code

JamesRein: /* Master Code */

2010-02-16T04:12:07Z

Master Code

JamesRein: /* Code */

2010-02-16T04:10:40Z

Code

JamesRein: /* Overview */

2010-02-16T03:20:55Z

Overview

JamesRein: /* Overview */

2010-02-16T03:19:54Z

Overview

@@ Line 1: / Line 1: @@
-== Original Assignment ==
-'''Do not erase this section!'''
-Your assignment is to create code that allows two PIC32s to communicate via I2C.
 == Overview ==

@@ Line 69: / Line 69: @@
  #pragma config FPBDIV = DIV_1				//Sets PBCLK to SYSCLK
- #define Fsck	50000      					//Frequency of (I2C) serial clock
+ #define Fsck	50000
+ #define BRG_VAL 	((PBCLK/2/Fsck)-2)
  #define Nop() asm( "nop" )                 //No-operation; asm stands for assembly, using an assembly command in C.  Cool!

@@ Line 349: / Line 349: @@
  		SlaveWriteI2C1(dataRead);
  	} else if ((I2C1STATbits.R_W == 1) && (I2C1STATbits.D_A == 1)) {
- 		// R/W bit = 1 --> indicates data transfer is input to slave
+ 		// R/W bit = 1 --> indicates data transfer is output from slave
  		// D/A bit = 1 --> indicates last byte was data
  		mLED_0_On();

@@ Line 341: / Line 341: @@
  	} else if ((I2C1STATbits.R_W == 1) && (I2C1STATbits.D_A == 0)) {
  		// R/W bit = 1 --> indicates data transfer is output from slave
- 		// D/A bit = 1 --> indicates last byte was address
+ 		// D/A bit = 0 --> indicates last byte was address
  		mLED_0_On();
  		mLED_2_Off();

@@ Line 7: / Line 7: @@
 == Overview ==
-[http://www.nxp.com/acrobat_download/literature/9398/39340011.pdf I2C] is pronounced "I squared C" and stands for Inter-Integrated Circuit.  This protocol was designed by Phillips Semiconductors around 1992 to allow easy communication between components on the same circuit board and can achieve transfer rates of up to 400 kbit/sec.  Is is a 2 line (plus common ground) communication method for one master device to control up to 112 slave devices.  While it is possible to have multiple masters on the same I2c bus, this page will only deal with a one master configuration.
+[http://www.nxp.com/acrobat_download/literature/9398/39340011.pdf I2C] is pronounced "I squared C" and stands for Inter-Integrated Circuit.  This protocol was designed by Phillips Semiconductors around 1992 to allow easy communication between components on the same circuit board and can achieve transfer rates of up to 400 kbit/sec.  I2C is a 2 line (plus common ground) communication method for one master device to control up to 112 slave devices.  While it is possible to have multiple masters on the same I2C bus, this page will only deal with a one master configuration.
 <b>Basic Operation</b>
@@ Line 34: / Line 34: @@
 The data line can only change while the clock line is low.  The data line is only read when the clock line is high and therefore 1 bit can be transferred per cycle of the clock line.
-The master is initially sends a start bit followed by the 7-bit address of the slave it wishes to communicate with. The next bit represents whether it wishes to write(0) to or read(1) from the slave.
+The master initially sends a start bit followed by the 7-bit address of the slave it wishes to communicate with. The next bit represents whether it wishes to write(0) to or read(1) from the slave.
 The slave then responds with an acknowledge bit. The transmission continues according to whether the master is attempting to read to or write from the device.

@@ Line 45: / Line 45: @@
 == Code ==
-In the code below, the master sends one of two bytes (0xAA or 0x23) to the slave at address 0x40. The slave then sends the byte back. If the slave receives a 0xAA, it lights its LEDs.
+In the code below, the master sends one of two bytes (0xAA or 0x23) to the slave at address 0x40. The master then receives a byte back from the slave. If the slave receives a 0xAA, it lights its LEDs.
+When the master begins sending, the slave triggers an interrupt (if the slave address is a match), which does one of four actions based on whether the master is reading or writing and whether the last byte was a data or address byte. As mentioned, when the master is writing the slave stores the byte, and when the master is reading the slave sends back the last stored byte.
 ===Master Code===
  /********************************************************

@@ Line 48: / Line 48: @@
 ===Master Code===
- /*******************************************************
+ /********************************************************
   * I2C_Master.c: Master code for I2C communication.	*
   * 	Both PICS use I2C1 module to send/ receive data.*
@@ Line 55: / Line 55: @@
   *							*
   * Hardware: 2 PIC32MX460F512L PICs on NU32 boards	*
-  *******************************************************
+  ********************************************************
   * Thomas Peterson, James Rein, Eric West		*
   * ME333 Winter 2010					*

@@ Line 19: / Line 19: @@
 |SCL1||Serial Clock Line||Output from master
 |-
-|SDA1||Data Line||Output from master
+|SDA1||Data Line||The single data line for sending/receiving
 |-
 |}
 The data line is read each time the clock line goes high, as shown in the diagram below: