Can't get SPI working

[asdf85]

Hi,

I've been trying to get the SPI communication working using the PIC16F873. I've browsed through the forum and nothing I try works.

I cant seem to get an output using the SPI_WRITE() command.

If i use the setup_spi() command, the microcontroller seems to stop working once it reaches the SPI_WRITE().

If i use the #USE SPI, the same thing happens unless i add the 'FORCE_HW', then it doesnt hang. However there is just no output even after i check the pin. I've tried it with and without the 'delay_ms' or 'delay_us'.
also, does the SCL and SDA pin require pull up resistors?

this is my code. May i know what im doing wrong? Im using compiler version 4.093
Thanks in advance

[Ttelmah]

Start with something really simple.
Write a 'toggle a pin' program, and test it first on C3, and then on C5. Do both pins toggle OK. If not, you have found a hardware problem...
If both don't work, then oscillator problem, MCLR problem etc..
If one works not the other, 'shorted wire'....

Then re-arrange your code slightly. Fuses should be above includes like STDIO.
Basically layout should always be:

Processor include
Fuses
Clock settings
Serial (if used)

Then general includes

Are you sure whatever you are using to detect the pulse train, would see it?.

Best Wishes

[asdf85]

Hi Ttelmah,

I've tested toggling both pins. What I notice is that if I remove the #USE SPI, those 2 pins toggles OK. But if #USE SPI is present, both those pins don't toggle.

I've also re-arranged my code but it still doesn't work.

I've also tried adding an ENABLE=PIN_B6 to the #USE SPI. There is a correct output coming out of pin b6 when I tested it, but nothing from SDO and CLK.

I'm pretty sure I should be able to see the pulse from SDO & CLK if there is one.

Any other ideas?

Thanks

[Ttelmah]

Not working, with #USE SPI present, is correct. The peripheral 'overrides' the pins. Means the peripheral _is_ being connected to the pins.

You say 'fairly sure'. With /16, on a 4MHz clock, the clock 'burst' will be eight cycles at 250KHz. Just 32uSec in duration. Doesn't take much to miss it.....
Try taking the division up to /64.

Best Wishes

[asdf85]

Thanks for the info.

The actual problem lied with the MCU I was using. After replacing it with another one, it worked.