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Stevo
Joined: 27 Mar 2015
Posts: 1
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| #USE SPI issue |
 Posted: Thu Jul 16, 2015 8:25 am |
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Hello All,
Hopefully a quick question. I'm working with a dsPIC33FJ256MC710A and Analog Device's AD7655 16 bit ADC.
My CCS C compiler version is: 5.026 with MPLAB 2.35
I'm using #USE SPI to setup the SPI2 Hardware on the dsPIC.
When I turn on my system it seems to print 0x0000 for roughly a minute or two then reports valid data. Is there a known bug with the #USE SPI for this compiler version, or am I just doing something incredibly stupid?
The Analog Devices' guy is pushing an SPI timing issue. but once it starts printing out valid data its stays valid for days - so i'm not wholly convinced.
Thanks in advance.
| Code: |
#include <33FJ256MC710A.h>
#include <STDlib.h>
#USE delay(internal=40MHz)
#USE RS232(BAUD=115200,XMIT=PIN_F3,RCV=PIN_F2,ERRORS)
#USE SPI(SPI2,FORCE_HW,MASTER,DI=PIN_G7,CLK=PIN_G6,MODE=1,BAUD=56200,XFER16) //ADC SPI Interface
//Rev. B Boards:
#define ADC_A0 PIN_B0 //Pin Definition for AD7655 MUX Select
#define ADC_CNVST PIN_E5 //Pin Definition for AD7655 Conversion Start
#define ADC_CS PIN_E6 //Pin Definition for AD7655 Chip Select
#define ADC_BUSY PIN_E7 //Pin Definition for AD7655 Busy Signal
int16 chanA = 0; //Channel A ADC Reading
int16 chanB = 0; //Channel B ADC Reading
void main(){
delay_ms(5000);
output_high(ADC_CS);
output_high(ADC_A0);
output_high(ADC_CNVST);
delay_ms(1000);
output_low(ADC_CS);
printf("TEST...TEST...TEST..");
delay_ms(2000);
while(TRUE){
output_low(ADC_CNVST); //Pulls Conversion Pulse low
delay_us(1); //Delay for Conversion Pulse
output_high(ADC_CNVST);
while(input_state(ADC_BUSY) == 1); //Waits for ADC to respond with end of conversion
delay_us(1);
delay_us(2);
chanA = SPI_READ2_16(0x0000); //Sends clock for SPI read (16 bit wide)
chanB = SPI_READ2_16(0x0000); //Sends clock for SPI read (16 bit wide)
delay_ms(1);
printf("%4X %4X",chanA,chanB);
chanA =0;
chanB =0;
delay_ms(2000);
}
}
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Ttelmah
Joined: 11 Mar 2010
Posts: 19451
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| Posted: Thu Jul 16, 2015 10:55 am |
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When using #use spi, you _must_ use spi_xfer, not spi_read or spi_write. It'll 'sort of work - sometimes' if you mix the two usages.
That you are doing a define to handle the 16bit transfer, suggests you are not using spi_xfer (spi_xfer can do a 16bit transfer). You don't show us though....
However, set the SPI up differently. Just use SPI2 (you don't need the pin numbers when this is used - selecting both is pointless). Also if the hardware is specified with SPI2, FORCE_HW is also pointless. Get rid of the XFER16 definition (not needed the default setting allows up to four bytes to be transferred), give the stream a name, and add the CS pin to the setup.
#USE SPI(SPI2, MASTER, MODE=1, BAUD=56200, ENABLE=PIN_E6, STREAM=ADC)
Then define the value as a 32bit variable, and
value = spi_xfer(ADC, value, 32);
will automatically operate the CS, and transfer 32bits as one transaction |
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guy
Joined: 21 Oct 2005
Posts: 297
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| Posted: Sat Jul 18, 2015 9:47 am |
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| Wild guess: the #delay doesn't fit the actual speed in which the chip is actually running, this resulting in the delays (delay_ms(5000) etc.) being much longer than excepted...? |
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