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ac34856
Joined: 14 Dec 2009
Posts: 33
Location: Wales
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| SPI Clock - how do I force on always ? |
 Posted: Thu Dec 17, 2009 8:13 am |
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Hi, can anyone help ?
I'm trying to force the clock on the SPI line from an 18F4620
to be present, I used the code below. So far I cant see a clock
or the SDO data when I do multiple writes.
Can anyone tell me in the general scheme of things where
I am going wrong ?
There is nothing connected to the PIC I just want to see the
data lines toggle with the scope connected before I connect
other H/W.
Also, the INT_SSP routine (for some reason) keeps triggering when
there is nothing connected. I am obviously missing something -
Rob
| Code: |
//
// Test routine for SPI clock
//
#include <18F4620.h>
#define SDI PIN_C4
#define SDO PIN_C5
#define SCL PIN_C3
#fuses HS, NOWDT, NOPROTECT, NOLVP, BROWNOUT, STVREN
#use DELAY(CLOCK=20000000)
#use RS232(BAUD=115200, PARITY=N, XMIT=PIN_C0, BITS=8, RESTART_WDT, STREAM=DEBUG)
#use SPI(MASTER, DI=SDI, DO=SDO, CLK=SCL, BAUD=115200, BITS=16, FORCE_HW)
static unsigned width=0;
#INT_SSP
void ssp_handler()
{
disable_interrupts(GLOBAL);
printf("\r\n Interrupt on SPI");
enable_interrupts(GLOBAL);
}
void main ()
{
unsigned count=0;
setup_adc_ports(NO_ANALOGS);
setup_adc_ports(ADC_OFF);
enable_interrupts(INT_SSP);
enable_interrupts(GLOBAL);
setup_spi(SPI_MASTER | SPI_L_TO_H); // | SPI_SS_DISABLED);
while(TRUE)
{
spi_write(0xff);
spi_write(0xff);
spi_write(0xff);
printf("\r\n Outputting SPI Clock ? : (%u retries) ", count);
count++;
output_high(PIN_D0);
delay_ms(100);
output_low(PIN_D0);
delay_ms(50);
}
} |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Thu Dec 17, 2009 8:34 am |
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According to the compiler manual, #use spi() is not intended to be used with spi_write(). You are using an
undefined combination of two SPI methods. |
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ac34856
Joined: 14 Dec 2009
Posts: 33
Location: Wales
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| Posted: Thu Dec 17, 2009 8:57 am |
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I read this also,
so how do I do a write with #use spi
and also how do I read ? |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Thu Dec 17, 2009 9:03 am |
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| I'm not using it for various reasons, but the manual is clear about spi_xfer(). |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Dec 17, 2009 1:46 pm |
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Your program is too complicated. Make a simple program that will
just put out SPI clock and data. Example:
| Code: |
#include <18F4620.h>
#fuses HS,NOWDT,NOPROTECT,BROWNOUT,PUT,NOLVP
#use delay(clock=20000000)
#define SPI_MODE_0 (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_1 (SPI_L_TO_H)
#define SPI_MODE_2 (SPI_H_TO_L)
#define SPI_MODE_3 (SPI_H_TO_L | SPI_XMIT_L_TO_H)
//===============================
main(void)
{
setup_spi(SPI_MASTER | SPI_MODE_0 | SPI_CLK_DIV_16);
while(1)
{
spi_write(0x55);
delay_us(100);
}
} |
| Quote: | #INT_SSP
void ssp_handler()
{
disable_interrupts(GLOBAL); // Not necessary
printf("\r\n Interrupt on SPI");
enable_interrupts(GLOBAL); // Very bad
} |
Don't ever do this. You have never seen us do this on the forum.
Read the forum and the PIC data sheet. Don't enable global interrupts
inside an interrupt service routine. |
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