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endocom
Joined: 05 Nov 2009
Posts: 1
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| Problem with i2c on 12F675 |
 Posted: Thu Nov 05, 2009 3:25 pm |
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J'utilise les routines I2C sur un PIC12F675. Or la routine, I2C_write(adresse) ne fonctionne pas correctement. Sur les 7 bits d'adresse, uniquement 6 sont envoyés et le 7ème est toujours à 0.
Avez vous le même problème ?
Merci de vos aides
Translation:
I use i2c routines on a PIC12F675. However the routine, i2c_write(address) does not function correctly. Of the 7 bits of address, only 6 are sent and 7th is always to 0. Have you seen this problem? Thank you for your assistance.
| Code: |
**********************************
* Code utilisé
**********************************
#include <12F675.h>
#device adc=8
#FUSES NOWDT //No Watch Dog Timer
#FUSES INTRC_IO //Internal RC Osc, no CLKOUT
#FUSES NOCPD //No EE protection
#FUSES NOPROTECT //Code not protected from reading
#FUSES NOMCLR //Master Clear pin used for I/O
#FUSES NOPUT //No Power Up Timer
#FUSES NOBROWNOUT //No brownout reset
#FUSES BANDGAP_HIGH
#use delay(clock=4000000)
#use rs232(baud=9600,parity=N,xmit=PIN_A3,rcv=PIN_A2,bits=8)
#define PIN_SDA PIN_A0
#define PIN_SCL PIN_A1
#use i2c(Master,sda=PIN_SDA,scl=PIN_SCL,force_sw)
//#use standard_io
BOOLEAN I2C_ready()
{
int1 ack;
delay_ms(10);
i2c_start();
ack = i2c_write(0x0F);
i2c_stop();
return !ack;
}
void write_I2C(BYTE address, BYTE data) {
while(!I2C_ready());
i2c_start();
i2c_write(0x0F);
i2c_write(address);
i2c_write(data);
i2c_stop();
}
BYTE read_I2C(BYTE address)
{
BYTE data;
while(!I2C_ready());
i2c_start();
i2c_write(0x78);
i2c_write(address);
i2c_start();
i2c_write(0x78);
data=i2c_read();
i2c_stop();
return(data);
}
void main()
{
BYTE data;
setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_OFF);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_256);
setup_timer_1(T1_DISABLED);
setup_comparator(NC_NC);
setup_vref(FALSE);
enable_interrupts(GLOBAL);
init_capteur();
// TODO: USER CODE!!
while(true)
{
data=read_I2C(0x33);
};
}
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Ttelmah
Guest
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| Posted: Thu Nov 05, 2009 3:50 pm |
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When you then try to talk to your device, you send an address of 0x78, which is a _write_ address. You then try to read from the same address.....
You do the opposite on your write routine, sending a 0xF, which is a read address, and then trying to write to this.
Is the device at address 0xE/0xF, or at 0x78/0x79?.
The first byte sent after an I2C start, is the device address coded as the seven upper bits followed by a single bit signifyng bus direction. This normally needs to be _low_ for the first transaction, so you can send the register number to be selected as the following byte. You then send data in subsequent bytes for the 'write'. For a read, you need to send a repeated start (you do), followed by the device _read_ address (low bit set), followed by the data reads.
With the wrong direction bit selected, there will be a bus conflict between the PIC, and the device....
Best Wishes |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Nov 05, 2009 5:38 pm |
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Also, post the manufacturer and part number of the i2c slave device
that is connected to the 12F675. |
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