Communicating pic16f876 to sensor4

[Einly]

Dear sir,

I've written another program using the bit-bang method. It is much longer. Communication between the pic and the sensor is Mode A.

May I know does the program below make sense?

#include <16f876.h>
#use delay (clock=20000000)
#fuses noprotect, nowdt, hs, nolvp

#byte PORTA = 5
#byte PORTB = 6
#byte PORTC = 7

#define SCLK PIN_C3
#define SDIO PIN_C4
#define PD PIN_C2

void init_sensor();
void write_address (byte register_address);
byte read_data (byte register_address);

void main()
{
byte address=0x02;
byte data;

set_tris_b(0);
set_tris_c(0);

init_sensor();

do
{
write_address(address);
delay_us(200);
read_data(address);
if(bit_test(data,7))
output_high(PIN_C0);
else
output_low(PIN_C0);
}while(1);
}

void init_sensor()
{
output_low(SCLK);
output_low(SDIO);
output_low(PD);
delay_ms(4);
output_high(SCLK);
output_high(SDIO);
output_high(PD);
delay_us(200);
output_low(PD);
delay_ms(4);
}

void write_address(byte register_address)
{
int i;
for(i=0;i<8;i++)
{
output_low(SCLK);
output_bit(SDIO,shift_left(register_address,1,0));
delay_us(3);
output_high(SCLK);
delay_us(3);
}
}

byte read_data(byte register_address)
{
int i;
byte data=0;
for(i-0;i<8;i++)
{
output_low(SCLK);
delay_us(3);
shift_left(data,1,input(SDIO));
output_high(SCLK);
delay_us(3);
return data;
}
}

Thanks for your help.

Einly
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This message was ported from CCS's old forum
Original Post ID: 9042

[johnpcunningham]

What is sensor4? Who makes it and what is the part number? Without that information, no one can help you becaus no one knows what the communication protocal should be.

Also, what problem are you having?

JC
___________________________
This message was ported from CCS's old forum
Original Post ID: 9057

[Einly]

:=What is sensor4? Who makes it and what is the part number? Without that information, no one can help you becaus no one knows what the communication protocal should be.
:=
:=Also, what problem are you having?
:=
:=JC

Sensor4 is an optical sensor manufactured by Agilent Technologies (Optical navigation), i.e. ADNS2051.

The problem that I have is I am not sure whether I can make 1 pin from the PIC chip output (to send address to the sensor) and after a very short period, changing it to input pin (to receive data sent by the sensor) by just changing "set_tris_b(0) to set_tris_b(0xff)"? Must I use FAST_IO?
___________________________
This message was ported from CCS's old forum
Original Post ID: 9062

[johnpcunningham]

I could not find the datasheet so I dont know if this is I2C, SPI, or a specific protocal for this chip.

Anyway, to answer your question; You can change the output to an input in enough time. Remember, you are controling the clock so you can pulse the clock and then get the serial data. I think you need to pulse the clock low then high; the data should be stable - more than likely the data is output on a falling edge so when you go low then high, the data has time to stabilize on the line. Probably something like this; (after sending address)

#byte PORTA = 0x05
#byte PORTB = 0x06
#byte PORTC = 0x07

#byte TRIS_A = 0x85
#byte TRIS_B = 0x86
#byte TRIS_C = 0x87

#define SCLK PIN_C3
#define SDIO PIN_C4
#define PD PIN_C2

#define bit0 0
#define bit1 1
#define bit2 2
#define bit3 3
#define bit4 4
#define bit5 5
#define bit6 6
#define bit7 7


char read_data()
{
int i;
byte data=0x00;

//MAKE SDIO AN INPUT
bit_set(tris_C, pin4);
delay_us(100);

for(i = 0;i < 8; i++)
{
output_low(SCLK);
delay_us(3);
output_high(SCLK);
delay_us(3);
shift_left(data,1,input(SDIO));
}

//MAKE SDIO AN output (default)
bit_clear(tris_C, pin4);
delay_us(100);

return data;
}
___________________________
This message was ported from CCS's old forum
Original Post ID: 9065