PIC32MX: I2C External RAM - Revision history

NickMarchuk at 20:35, 1 March 2010

2010-03-01T20:35:25Z

NickMarchuk at 20:15, 1 March 2010

2010-03-01T20:15:56Z

NoahPentelovitch: /* Code */

2010-02-16T18:51:17Z

Code

NoahPentelovitch: /* Code */

2010-02-16T18:50:34Z

Code

NoahPentelovitch: /* Code */

2010-02-16T18:45:33Z

Code

NoahPentelovitch: /* Code */

2010-02-16T12:23:42Z

Code

NoahPentelovitch: /* Code */

2010-02-16T12:20:01Z

Code

NoahPentelovitch: /* Overview */

2010-02-16T12:11:39Z

Overview

TylerJohnson: /* Code */

2010-02-16T08:00:58Z

Code

Show changes

TylerJohnson: /* Circuit */

2010-02-16T02:26:43Z

Circuit

← Older revision		Revision as of 20:35, 1 March 2010
Line 1:		Line 1:
			'''DO NOT USE THE FOLLOWING CODE AS WRITTEN - IT DOES NOT WORK - MODIFY BEFORE USING'''

	== Overview ==		== Overview ==

@@ Line 1: / Line 1: @@
-== Original Assignment ==
-'''Do not erase this section!'''
-Use I2C communication to send data from the PIC32 to a PCF8570P SRAM chip.
 == Overview ==

@@ Line 91: / Line 91: @@
  // READ DATA FROM RAM
  //First sends write command to write which word the PIC wants to read from
- i2cData[0] = (SlaveAddress << 1) | 1;
+ i2cData[0] = ((SlaveAddress << 1) | 0);
  i2cData[1] = 0x05;
  DataSz = 2;

@@ Line 91: / Line 91: @@
  // READ DATA FROM RAM
  //First sends write command to write which word the PIC wants to read from
- i2cData[0] = (SlaveAddress << 1) | 0;
+ i2cData[0] = (SlaveAddress << 1) | 1;
  i2cData[1] = 0x05;
  DataSz = 2;

@@ Line 57: / Line 57: @@
  }
+ // WRITE TO SLAVE
  int main(void)
  {
@@ Line 89: / Line 89: @@
  IdleI2C1();
- //Reading Data from the PCF8570P
+ // READ DATA FROM RAM
  //First sends write command to write which word the PIC wants to read from
  i2cData[0] = (SlaveAddress << 1) | 0;

@@ Line 66: / Line 66: @@
  	int  DataSz;
  	//Enable channel
-	OpenI2C1( I2C_EN, BRG_VAL );
+        OpenI2C1( I2C_EN, BRG_VAL );
  SlaveAddress = 0x50; (0b01010000)
  i2cData[0] = ((SlaveAddress << 1) | 0 ); //slave address and write command
@@ Line 72: / Line 72: @@
  i2cData[2] = 0xAA; //data bits 10101010
  DataSz = 3;
-	StartI2C1();	//Send the Start condition to the clock and data lines
+  StartI2C1();	//Send the Start condition to the clock and data lines
-	IdleI2C1();		//Wait to complete
+  IdleI2C1();		//Wait to complete
  MasterWriteI2C1 (i2cData[0]); //sends first string of data to PCF8570P
  IdleI2C1();
-	if( I2C1STATbits.ACKSTAT ) //looks for acknowledge low bit to be returned
+  if( I2C1STATbits.ACKSTAT ) //looks for acknowledge low bit to be returned
-			break;
+   break;
  MasterWriteI2C1 (i2cData[1]);
  IdleI2C1();
-	if( I2C1STATbits.ACKSTAT )
+  if( I2C1STATbits.ACKSTAT )
-			break;
+   break;
  MasterWriteI2C1 (i2cData[2]);
  IdleI2C1();
-	if( I2C1STATbits.ACKSTAT )
+  if( I2C1STATbits.ACKSTAT )
-			break;
+   break;
  StopI2C1(); //sends the stop condition to the PCF8570P clock and data lines
  IdleI2C1();
@@ Line 94: / Line 94: @@
  i2cData[1] = 0x05;
  DataSz = 2;
-	StartI2C1();	//Send the Start Bit
+  StartI2C1();	//Send the Start Bit
-	IdleI2C1();		//Wait to complete
+   IdleI2C1();	//Wait to complete
  MasterWriteI2C1 (i2cData[0]);
  IdleI2C1();
-	if( I2C1STATbits.ACKSTAT )
+  if( I2C1STATbits.ACKSTAT )
-			break;
+   break;
  MasterWriteI2C1 (i2cData[1]);
  IdleI2C1();
-	if( I2C1STATbits.ACKSTAT )
+  if( I2C1STATbits.ACKSTAT )
-			break;
+   break;
  RestartI2C1(); //restarts the PCF8570P
  IdleI2C1();
  MasterWriteI2C1( (SlaveAddress << 1) | 1 ); //transmit slave address and read command
-	IdleI2C1();
+  IdleI2C1();
  MasterWriteI2C1(i2cData[1]);
-	IdleI2C1();
+  IdleI2C1();
  unsigned char i2cbyte;
-	i2cbyte = MasterReadI2C1(); //PIC reads data from PCF8570P
+  i2cbyte = MasterReadI2C1(); //PIC reads data from PCF8570P
  StopI2C1();
  IdleI2C1();

@@ Line 28: / Line 28: @@
  // INCLUDES
  #include <HardwareProfile.h>
  #include <HardwareProfile_NU32.h>
  #include <plib.h>
  // Configuration Bit settings
  // SYSCLK = 80 MHz (8MHz Crystal/ FPLLIDIV * FPLLMUL / FPLLODIV)
@@ Line 44: / Line 42: @@
  // DEFINES
  #define SYSCLK	(80000000)
  #define PBCLK  (SYSCLK/2) // set PBCLK to 800 KHz
  #define Fsck	50000
  #define BRG_VAL 	((PBCLK/2/Fsck)-2)
  #define Nop() asm( "nop" )
- /////////////////////////////////////////////
  void i2c_wait(unsigned int cnt)
@@ Line 64: / Line 57: @@
  }
- /////////////////////////////////////////////
  int main(void)
  {
  while(1)
@@ Line 74: / Line 65: @@
  	char i2cData[0];
  	int  DataSz;
  	//Enable channel
 	OpenI2C1( I2C_EN, BRG_VAL );
  SlaveAddress = 0x50; (0b01010000)
  i2cData[0] = ((SlaveAddress << 1) | 0 ); //slave address and write command
  i2cData[1] = 0x05; //word address
  i2cData[2] = 0xAA; //data bits 10101010
  DataSz = 3;
 	StartI2C1();	//Send the Start condition to the clock and data lines
 	IdleI2C1();		//Wait to complete
  MasterWriteI2C1 (i2cData[0]); //sends first string of data to PCF8570P
  IdleI2C1();
 	if( I2C1STATbits.ACKSTAT ) //looks for acknowledge low bit to be returned
 			break;
  MasterWriteI2C1 (i2cData[1]);
  IdleI2C1();
 	if( I2C1STATbits.ACKSTAT )
 			break;
  MasterWriteI2C1 (i2cData[2]);
  IdleI2C1();
 	if( I2C1STATbits.ACKSTAT )
 			break;
  StopI2C1(); //sends the stop condition to the PCF8570P clock and data lines
  IdleI2C1();
- ///////////////////////////////////////////////////////////
  //Reading Data from the PCF8570P
  //First sends write command to write which word the PIC wants to read from
  i2cData[0] = (SlaveAddress << 1) | 0;
  i2cData[1] = 0x05;
  DataSz = 2;
 	StartI2C1();	//Send the Start Bit
 	IdleI2C1();		//Wait to complete
  MasterWriteI2C1 (i2cData[0]);
  IdleI2C1();
 	if( I2C1STATbits.ACKSTAT )
 			break;
  MasterWriteI2C1 (i2cData[1]);
  IdleI2C1();
 	if( I2C1STATbits.ACKSTAT )
 			break;
  RestartI2C1(); //restarts the PCF8570P
  IdleI2C1();
  MasterWriteI2C1( (SlaveAddress << 1) | 1 ); //transmit slave address and read command
 	IdleI2C1();
  MasterWriteI2C1(i2cData[1]);
 	IdleI2C1();
  unsigned char i2cbyte;
 	i2cbyte = MasterReadI2C1(); //PIC reads data from PCF8570P
  StopI2C1();
  IdleI2C1();
  }
  }

@@ Line 8: / Line 8: @@
 This page discusses work toward sending data to a PCF8570P SRAM chip. Basic I2C communication information, chip data, circuit diagram, and a partially functioning code are given. Prior to the code is a brief explanation of where the code is failing and why no data is being transmitted between the PIC 32 and the PCF8570P.
+Data is sent to the PCF8570 SRAM chip by first sending a 7-bit slave address, then a 8-bit write address and then 8-bit data strings. The eighth bit in the slave address is set to either a 0 (write) or 1 (read) which tells the master and the slave what operation is happening. After each string is sent, there is a ninth bit which is the acknowledge bit. This bit is set low if the master or slave receives the information (acknowledge) or high if they do not (not acknowledge).
 == Circuit ==

@@ Line 15: / Line 15: @@
 The PCF8570P chip has a built-in 4 bit hardware address and 3-bit user-defined hardware address allowing multiple chips to be on the same I2C data line. The diagram below shows the following 7-bit hardware address (bits shown in '''bold''' are given by the manufacturer: '''1010'''010
-[[Image:circuit.jpg]]
+[[Image:I2C_RAM.jpg]]
 == Code ==