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cleberalbert
Joined: 25 Feb 2014
Posts: 34
Location: Brazil
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| 16 bits I2C communication between 2 PICs 18F |
 Posted: Thu Jul 31, 2014 2:51 pm |
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This program is to provide 16 bits I2C communication between 2 PICs 18F. The code was done on CCS 5.018, it's commented and working. Tested with PIC18F4520.
Master.c
| Code: |
#include <18f4520.h>
#fuses HS
#fuses PUT
#fuses NOWDT //No Watch Dog Timer
#fuses NOBROWNOUT //No brownout reset
#fuses NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#fuses NOXINST //Extended set extension and Indexed Addressing mode disabled (Legacy mode)
#use delay(crystal=20MHz)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS) //+++ up baud rate?
#use i2c(master, sda=PIN_C4, scl=PIN_C3, FORCE_HW)
/* Bit defines */
#define EEPROM_SCL PIN_C3
#define EEPROM_SDA PIN_C4
#define SLAVE_ADDRESS 0x20 // addr=2 reserved, note address masking.
#define I2C_DELAY_US 16 // worked 20 //Worked 32 //75 //100
#define I2C_INTERBYTE_DELAY_US 60 // worked 80
#byte PIC_SSPCON2 = 0xfc5
void initI2C (void);
void writeI2C (int16 word, unsigned int slave_addr);
int16 readI2C (unsigned int slave_addr);
int16 mainI2C ();
void initI2C (void)
{
output_float(EEPROM_SCL);
output_float(EEPROM_SDA);
}
void writeI2C (int16 word, unsigned int slave_addr)
{
i2c_start();
delay_us(I2C_DELAY_US);
i2c_write(slave_addr); /* Device Address */
delay_us(I2C_DELAY_US);
i2c_write(word & 0x00ff); //LSB first
delay_us(I2C_DELAY_US);
i2c_write((word & 0xff00) >> 8); //MSB second
delay_us(I2C_DELAY_US);
i2c_stop();
delay_us(I2C_DELAY_US);
}
int16 readI2C (unsigned int slave_addr)
{
int8 b1=0, b2=0;
i2c_start(); // restart condition
delay_us(I2C_DELAY_US);
i2c_write(slave_addr + 1);
delay_us(I2C_INTERBYTE_DELAY_US);
b1 = i2c_read(1);
delay_us(I2C_INTERBYTE_DELAY_US);
b2 = i2c_read(0);
delay_us(I2C_DELAY_US);
i2c_stop();
return make16(b2, b1);
}
void main(){
int16 data_to_send=18099;
int16 data_received;
initI2C();
delay_ms(10);
// Write
writeI2C(data_to_send, SLAVE_ADDRESS);
printf("Message sent successfully from the Master to the Slave: %ld\n",data_to_send);
// Read
data_received = readI2C(SLAVE_ADDRESS);
printf("Answer received successfully from the Slave to the Master: %ld\n",data_received);
printf("\n");
}
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Slave.c
| Code: |
#include <18f4520.h>
#fuses HS
#fuses PUT
#fuses NOWDT //No Watch Dog Timer
#fuses NOBROWNOUT //No brownout reset
#fuses NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#fuses NOXINST //Extended set extension and Indexed Addressing mode disabled (Legacy mode)
#use delay(crystal=20MHz)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#use i2c(Slave, Slow, sda=PIN_C4, scl=PIN_C3, force_hw, address=0x20)
/* PIC Registers */
#byte SSPBUF = 0xfc9
#byte SSPADD = 0xfc8
#byte SSPSTAT = 0xfc7
#byte SSPCON1 = 0xfc6
#byte SSPCON2 = 0xfc5
#byte PIE1 = 0xf9d
#byte TRISC = 0xf94
int16 data_to_send=18100; //In the next step of the code development this data is going to change every loop (sensor data)
int16 data_sent;
int16 data_received;
#int_SSP
void i2c_interrupt() {
//Get state
int state;
int writeBuffer[2];
int readBuffer[2];
state = i2c_isr_state();
if(state==0) //Address match received with R/W bit clear, perform i2c_read( ) to read the I2C address.
i2c_read();
else if (state==0x80) //Address match received with R/W bit set; perform i2c_read( ) to read the I2C address, and use i2c_write( ) to pre-load the transmit buffer for the next transaction (next I2C read performed by master will read this byte).
i2c_read(2);
if (state>=0x80) //Master is waiting for data
{
writeBuffer[0] = (data_to_send & 0xFF); //LSB first
writeBuffer[1] = ((data_to_send & 0xFF00)>>8); //MSB secound
i2c_write(writeBuffer[state - 0x80]); //Write appropriate byte, based on how many have already been written
if ((state-0x80)==2){
data_sent=make16(writeBuffer[1],writeBuffer[0]);
printf("\nFull data sent: %ld\n",data_sent);
}
}
else if(state>0) //Master has sent data; read.
{
readBuffer[state - 1] = i2c_read(); //LSB first and MSB secound
if (state==2){
data_received=make16(readBuffer[1],readBuffer[0]);
printf("\nFull data received: %ld\n",data_received);
}
}
}
void main() {
enable_interrupts(INT_SSP); //Enable interrupts
enable_interrupts(GLOBAL);
i2c_slaveAddr(0x20);
while (TRUE)
delay_us(10);
}
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emazzu630
Joined: 14 Aug 2018
Posts: 20
Location: Ouro Verde - SC
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| Comunicação I2C de 16 bits entre 2 PICs 18F |
| Posted: Mon Oct 28, 2019 2:15 pm |
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I was looking at Google for support to implement I2C and found this post.
The code is exactly what I need, but I had a hard time assembling the
circuit diagram ... Please if anyone has access to the Proteus file or
simply the schematic, I really need it. You can send me by the following
emails: euclidesmz@hotmail.com, euclidesmz@gmail.com |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Oct 28, 2019 6:15 pm |
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The hardware schematic looks like this:
https://i.stack.imgur.com/SdGJy.jpg
Connections are from SCL to SCL, and SDA to SDA, with a 4.7K pull-up
resistor on each one. The pull-up voltage is the same as the PIC's Vdd.
In the schematic shown, it is +5 volts. |
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