Problem width MCP3302(A/D Converter)

[kaos]

Halo, my english is very poor so I ask for pardon.

hardware:

MCP3301 -> 13-Bit Differential Input, Low Power A/D Converter with SPI™ Serial Interface (microchip)



PIC18F2550

code:

[RolandAldridge]

I think you have the chip select lines the wrong way up - bring it low while you write to or read from it, high when you are not doing so.

Here is my code for a 3204, using a 16C67:

byte first_data_out, second_data_out;
struct adc_data_type{ byte hi; byte lo;} adc_data;
long data_in = 0;
first_data_out = 0x06; // See MP3204 data sheet

// Set up the data_out byte to tell the ADC what channel to look at.
If (ADC_Channel > 3) ADC_Channel = 0; // We'll look at the reading, what the hell
second_data_out = ADC_Channel << 6; // 0 is oxygen, 1 is Alarm 1, 2 is Alarm 2, 3 is span value
setup_spi(SPI_MASTER|SPI_L_TO_H|SPI_CLK_DIV_16|SPI_SS_DISABLED);
//Set up the SPI for 0,0 operation
CKE = TRUE; // data out transmitted on clock rising edge
SMP = FALSE; // input data sampled in middle of data output time

// set the /cs pin high then low to initiate communication
// Output_HIGH(ADC_CS);
Output_LOW(ADC_CS);

//Now tell it what we want
//Dump any data in the buffer
If ( SPI_DATA_IS_IN() )data_in = spi_read();
// Write the command data into the chip
SPI_write(first_data_out);
adc_data.lo = SPI_read(); // garbage
SPI_write(second_data_out);
adc_data.hi = spi_read(); // of which the first four bits are garbage
SPI_write(second_data_out); // so as to clock in the lower byte
adc_data.lo = spi_read();
adc_data.hi &= 0x0F; // Dump the top four bits
data_in = adc_data.hi;
data_in <<= 8;
data_in += adc_data.lo;

Output_HIGH(ADC_CS); // set the /cs high again

return( data_in);

Roland
_________________
Roland Aldridge
www.amio2.com

[nina]

what means these lines?

byte_high <<3>>= 3;
return (make16(byte_high,byte_low));

tks

[kaos]

In the picture you can to see that 3 bytes don't use so first, <<3, move 3 bytes to left an them, >>3, move 3 bytes to right. Now there is 0.

[nina]

kaos...

why do I need use this line?

tks

[Humberto]

[kaos]

It does not work. I dont't understand, because the A/d is very simple but only send 514 and dont change.

Thank you anyhow.

pd:

I writed

byte_high <<= 3;
byte_high >>= 3;

but the foro changed it ;).