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ymoona
Joined: 20 Mar 2005
Posts: 32
Location: Heiloo, the Netherlands
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| 16F88 I2C master slave problem |
 Posted: Thu Nov 13, 2008 3:17 pm |
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Hi,
I'm using two 16F88 to communicate via i2c.
The master is reading two bytes, the slave is writing two bytes.
I'm using version 4.013.
This is the master code
| Code: |
#include <16F88.h>
#device *=16
#device adc=10
#FUSES NOWDT //No Watch Dog Timer
#FUSES INTRC_IO //Internal RC Osc, no CLKOUT
#FUSES PUT //No Power Up Timer
#FUSES MCLR //Master Clear pin enabled
#FUSES BROWNOUT //Reset when brownout detected
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES NOWRT //Program memory not write protected
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOPROTECT //Code not protected from reading
#FUSES FCMEN //Fail-safe clock monitor enabled
#FUSES IESO //Internal External Switch Over mode enabled
#use delay(clock=8000000)
#use rs232(baud=19200,parity=N,xmit=PIN_B5,rcv=PIN_B2,bits=8)
#use i2c(Master,sda=PIN_B1,scl=PIN_B4)
int8 address;
#int_RDA
RDA_isr()
{
char c;
c = getc();
putc( c );
}
#define LED_RED PIN_A4
#define LED_YELLOW PIN_A3
#define LED_GREEN PIN_A2
#define SLAVE 0xA0
void main()
{
int byte1, byte2;
setup_adc_ports(sAN0|VSS_VDD);
setup_adc(ADC_CLOCK_INTERNAL);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DIV_BY_16,2,4);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
setup_oscillator(OSC_8MHZ);
delay_ms( 100 );
printf("\f");
while(1){
output_high( LED_GREEN );
delay_ms( 500 );
output_low( LED_GREEN );
delay_ms( 500 );
i2c_start();
putc('S');
i2c_write(SLAVE + 1);
putc('W');
byte1 = i2c_read();
putc('R');
byte2 = i2c_read(0);
putc('R');
i2c_stop();
putc('T');
printf( " byte1=%02x, byte2=%02x\n\r" , byte1, byte2 );
}
}
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Why MUST the second i2c_read be called with an argument 0? If I dont do that the master will hang.
This is the slave code
| Code: |
#include <16F88.h>
#device *=16
#device adc=10
#FUSES NOWDT //No Watch Dog Timer
#FUSES INTRC_IO //Internal RC Osc, no CLKOUT
#FUSES PUT //No Power Up Timer
#FUSES NOMCLR //Master Clear pin enabled
#FUSES BROWNOUT //Reset when brownout detected
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES NOWRT //Program memory not write protected
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOPROTECT //Code not protected from reading
#FUSES FCMEN //Fail-safe clock monitor enabled
#FUSES IESO //Internal External Switch Over mode enabled
#use delay(clock=8000000)
#use rs232(baud=19200,parity=N,xmit=PIN_B5,rcv=PIN_B2,bits=8)
#use i2c(Slave,sda=PIN_B1,scl=PIN_B4,address=0xA0)
#define LED_RED PIN_A4
#define LED_YELLOW PIN_A3
#define LED_GREEN PIN_A2
#int_RDA
RDA_isr()
{
char c;
c = getc();
putc( c );
}
unsigned int incomming = 0, state;
#int_SSP
SSP_isr()
{
//putc('.');
state = i2c_isr_state();
if( state < 0x80)
{
}
if(state >= 0x80)
{
if(state == 0x80){
OUTPUT_TOGGLE( LED_GREEN );
putc('1');
i2c_write(0x56);
}
else if(state == 0x81){
OUTPUT_TOGGLE( LED_YELLOW );
i2c_write(0x1F);
putc('2');
}
else if(state == 0x82){
OUTPUT_TOGGLE( LED_RED );
i2c_write(0x45);
putc('3');
}
}
}
void main()
{
setup_adc_ports(sAN0|VSS_VDD);
setup_adc(ADC_CLOCK_INTERNAL);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DIV_BY_16,2,4);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
enable_interrupts(INT_RDA);
enable_interrupts(INT_SSP);
enable_interrupts(GLOBAL);
setup_oscillator(OSC_8MHZ);
delay_ms(100);
printf("\f");
while(1){
delay_ms( 1000 );
}
}
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Now the data is read fine, but in the terminal of the slave I see on every read action of the master "123". Also the three leds toggle. Indicating to
me that 3 bytes are read.
When I put a putc('.'); in the beginning of the ISR I get ".1.2" in the terminal of the slave. Indicating to me that only two bytes are read.
What am I doing wrong, can
_________________
checkout my site: www.ymoona.com/wiki |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Nov 13, 2008 3:29 pm |
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| Quote: | | Why MUST the second i2c_read be called with an argument 0? |
It's part of the i2c specification. You can download it here:
http://www.nxp.com/acrobat_download/literature/9398/39340011.pdf
Look in this section, on the right side of the page:
It says what an i2c master must do when it's clocking bytes out of
the slave:
| Quote: | If a master-receiver is involved in a transfer, it must signal
the end of data to the slave-transmitter by not generating
an acknowledge on the last byte that was clocked out of
the slave. The slave-transmitter must release the data line
to allow the master to generate a STOP or repeated
START condition. |
In CCS, a "not acknowledge" is generated by using a 0 parameter
in the i2c_read() statement. |
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ymoona
Joined: 20 Mar 2005
Posts: 32
Location: Heiloo, the Netherlands
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| Posted: Thu Nov 13, 2008 3:42 pm |
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Thanks, that makes sense.
Do you also have an answer to my other questions?
_________________
checkout my site: www.ymoona.com/wiki |
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