# SPI Problems
**URL:** https://forums.digi.com/t/spi-problems/11125
**Category:** Rabbit
**Created:** [September 7, 2009, 8:01am UTC](https://forums.digi.com/t/spi-problems/11125 "2009-09-07T08:01:04Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@newbie](https://forums.digi.com/u/newbie)
#### Post date: [September 7, 2009, 8:01am UTC](https://forums.digi.com/t/spi-problems/11125/1 "2009-09-07T08:01:04Z")
Hi,
I m working with this RCM4500 and using this SPI function but it didint seen to work. i read some of the post and notice that the comment was to us Serial B instead of serial C. but i have already use Serial B for my xbee.
## Was serial C not competible for SPI? i used and edited they sample coding given:
#class auto
#define SPI\_SER\_C
#define SPI\_CLK\_DIVISOR 100
#use “spi.lib”
void main()
{
char adc\_reading[2];
int i;
int adc\_sample;
```
SPIinit();
while(1)
{
SPIWrite("\x05", 1); \\ cmd to write to register
SPIRead(adc_reading, 2);
printf("SPI bytes = 0x%x 0x%x
```
## ", adc\_reading[0], adc\_reading[1]); } }
I always got a 0xff or 0x00
Or is my pin configuration wrong? Below is my configuration:
PC3 connected to Dout of my SPI component
PC2 connected to Din of my SPI component
PD2 connected to SCLK of my SPI component
---
### Author:  [@sgt](https://forums.digi.com/u/sgt)
#### Post date: [September 7, 2009, 3:39pm UTC](https://forums.digi.com/t/spi-problems/11125/2 "2009-09-07T15:39:15Z")
What about chip select? I’ve got some devices here that will not work if you just ground /CS…
Haven’t used SPI.LIB myself - I just roll my own - so I can’t speak to that aspect of it. I do use serial port C as an SPI port though (this is on an RCM 5700, not 4500), so there should be no problem there.
Another thing to look at: You haven’t shown your port initialization. Have you set up Serial Port C to map to the pins you are using?
---
### Author:  [@system](https://forums.digi.com/u/system)
#### Post date: [November 22, 2009, 6:18am UTC](https://forums.digi.com/t/spi-problems/11125/3 "2009-11-22T06:18:25Z")
Whyd you need to throw in the part about telling Mike you wouldnt post about this then turn around and did just that?
Ive not had any problems.
---
### Author:  [@newbie](https://forums.digi.com/u/newbie)
#### Post date: [September 8, 2009, 9:13am UTC](https://forums.digi.com/t/spi-problems/11125/4 "2009-09-08T09:13:20Z")
## Thanks for your quite respond. Initalising? To do u mean this?
```
#define SPI_DR SCDR
#define SPI_CR SCCR
#define SPI_ShCR SCCRShadow
#define SPI_SR SCSR
#define SPI_ER SCER
#define SPI_ShER SCERShadow
WrPortI ( SCDHR, NULL, (SPIdivisor>>8) | 0x80 );
WrPortI ( SCDLR, NULL, SPIdivisor & 0xFF );
```
* * *
its defined in the spi library.
Ok i will connect tthe chipselect and see if it works.
---
### Author:  [@sgt](https://forums.digi.com/u/sgt)
#### Post date: [September 8, 2009, 4:24pm UTC](https://forums.digi.com/t/spi-problems/11125/5 "2009-09-08T16:24:55Z")
By initializing, I’m referring to setting up the parallel ports. Like this, which won’t be exactly what you need to do, but should give you the idea:
```auto
// Parallel Port C Setup
WrPortI(PCDDR, &PCDDRShadow, (PCDDRShadow & 0xF3) | 0x0C); // PC2 & 3 are outputs
WrPortI(PCALR, &PCALRShadow, (PCALRShadow & 0xCF) | 0x00); // PC2: Alt out 0 (TxC)
WrPortI(PCFR, &PCFRShadow, (PCFRShadow & 0xF3) | 0x04); // PC2 alt out, PC3 norm
// Parallel Port D Setup
WrPortI(PDDDR, &PDDDRShadow, (PDDDRShadow & 0xF3) | 0x0C); // PD2, 3 are outputs
WrPortI(PDALR, &PDALRShadow, (PDALRShadow & 0xCF) | 0x00); // PD2: Alt out 0 (SCLKC)
WrPortI(PDFR, &PDFRShadow, (PDFRShadow & 0xF3) | 0x04); // PD2 alt out, PD3 norm
```
The registers are described in the Microprocessor User’s Manual for whatever processor you are using.
---
### Author:  [@sam2](https://forums.digi.com/u/sam2)
#### Post date: [October 8, 2009, 10:08am UTC](https://forums.digi.com/t/spi-problems/11125/6 "2009-10-08T10:08:39Z")
Hi, im also trying out the spi in rabbit, im trying to connect it with a adc, so basically what pins do i need to wired out to the rabbits port…
Vcc to +3.3V
Gnd to Gnd
SCLK to SCLKA
Chip Selection to Any Output Port
Data out to TxB
Data In to RxB
is it something like this?