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CCS SPI functions

 
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lloureiro



Joined: 19 Sep 2012
Posts: 9

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CCS SPI functions
PostPosted: Wed Sep 19, 2012 3:31 am     Reply with quote

Hello to everyone.

I'm new using CCS SPI library and i have one question:

after using setup_spi, spi is ready to use?

no more settings?


I´m using pic16f886 to read ADXL345 values but get nothing. I put a scope at pin14 (RC3/SCK/SCL) and don't see clock activity.
I'm using CCS demo with MPLAB plugin.

There is my code:
Code:

#include "../h/ring.h"
#use delay(clock=8000000)
#include "../h/fuses.h" 
#use rs232(baud=1200, xmit=PIN_B6, rcv=PIN_B7) 

 void init(){             
   setup_oscillator(OSC_8MHZ);
   SET_TRIS_B(0x82);
   setup_timer_1(T1_INTERNAL | T1_DIV_BY_8);//
   setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_XMIT_L_TO_H  | SPI_CLK_DIV_64  );//
   SET_TRIS_C(0x00); //
   spi_write(0x31); //send the write instruction
   //spi_write(0x01); //address of a register to test reading and writing  //
     spi_write(0x2D); //send the write instruction//
    spi_write(0x08); //address of a register to test reading and writing 
}     

    void main (){
      init();
      printf( "teste");
      char x0;
      setup_timer_1(T1_INTERNAL | T1_DIV_BY_8);
      set_timer1(0);
      for(;;){
      OUTPUT_LOW(PIN_C0);
      delay_us(5);
      x0= spi_read(0x32); //send the write instructio;           
      OUTPUT_HIGH(PIN_C0);
      printf( "valor %c\r\n", x0);
      delay_ms(1000);
     }
     }

To read adxl345, is enough using write and read spi functions?

Regards,

Luis Loureiro


Last edited by lloureiro on Wed Sep 19, 2012 5:42 am; edited 2 times in total
temtronic



Joined: 01 Jul 2010
Posts: 9081
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PostPosted: Wed Sep 19, 2012 5:21 am     Reply with quote

welcome !!
You should always tell us the PIC type and the compiler version and post a small, compilable program that shows the problem as it's near impossible to decide where or what your problem is. Could be a compiler bug (rare), PIC variant (not all PICs are the same) or hardware (testing wrong pin, miswired,..), etc.

Also, check the examples folder that CCS supplies, to see how they setup/use the SPI module of the PICs. They've supplied LOTS of great examples you can run/use/modify !!

You can search this forum as well, using 'SPI' to see hits of similar SPI problems. Odds are good you're NOT the first one having the 'problem'!!

hth
jay
lloureiro



Joined: 19 Sep 2012
Posts: 9

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not the firts and not the last...
PostPosted: Wed Sep 19, 2012 5:44 am     Reply with quote

...but i searched i didn't found a problem like my problem Smile

Thanks
asmboy



Joined: 20 Nov 2007
Posts: 2128
Location: albany ny

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PostPosted: Wed Sep 19, 2012 7:31 pm     Reply with quote

Code:

for(;;){
      OUTPUT_LOW(PIN_C0);
      delay_us(5);
      x0= spi_read(0x32); //send the write instructio;           
      OUTPUT_HIGH(PIN_C0);
      printf( "valor %c\r\n", x0);
      delay_ms(1000);


the above is what you want to use as your accelerometer driver???

and you have read and UNDERSTAND the datasheet for the part?

as in where is your management code for the NOT CS line of the ADXL ??
( as follows ??)
Code:

spi_write(0x31); //send the write instruction
   //spi_write(0x01); //address of a register to test reading and writing  //
     spi_write(0x2D); //send the write instruction//
    spi_write(0x08); //address of


you are sure you are handling the right pins etc etc??
lloureiro



Joined: 19 Sep 2012
Posts: 9

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PostPosted: Thu Sep 20, 2012 1:51 am     Reply with quote

Hello,

I change my code, and now it is:

//init

Code:
#define ACC1_SELECT PIN_C0
#define ADXL345_ADDR_WRITE     0xA6
#define ADXL345_ADDR_READ     0xA7

Code:
   ...
                setup_oscillator(OSC_8MHZ);
   SET_TRIS_B(0x82);
   SET_TRIS_C(0x10);
                setup_spi(SPI_MASTER | SPI_MODE_3 | SPI_CLK_DIV_4 );
   accelerometer_init2();
               ....


where mode 3 is:
Code:
 #define SPI_MODE_3  (SPI_H_TO_L | SPI_XMIT_L_TO_H)


and the init method:

Code:
void accelerometer_init2(void)
{

   output_low(ACC1_SELECT);
    spi_write(ADXL345_ADDR_WRITE);     
    spi_write(ADXL345_POWER_CTL);      ´
      spi_write(0x00);                     
spi_write(ADXL345_ADDR_WRITE);   
      spi_write(ADXL345_POWER_CTL);       
   spi_write(0x08);                     
spi_write(ADXL345_ADDR_WRITE);         
 spi_write(0x31);           
      spi_write(0x00);                   
   output_high(ACC1_SELECT);

}

and i run a selt test that exists on device:

Code:

int16 x_test(void)
{     

   unsigned char dummy=0;
    unsigned char xh=0;
 unsigned char   xl=0;
   int16 xo=0;

   output_low(ACC1_SELECT);
   spi_write(ADXL345_ADDR_WRITE);   
   spi_write(0x31);               
   spi_write(0x80);               
   output_high(ACC1_SELECT);

   output_low(ACC1_SELECT);
   spi_write(ADXL345_ADDR_WRITE);   
   spi_write(ADXL345_DATAX0);       

   xl = spi_read();         
   spi_write(ADXL345_ADDR_WRITE);   
   spi_write(ADXL345_DATAX1);       
 
   xh = spi_read();           
   output_high(ACC1_SELECT);

   xo = xl|(xh << 8);             
   return xo;
}


and always get the value of "0".

And i used a scope, i can see pic pulses on sdo of pic but i don't see any clock activity of pic?
Something wrong with this clock setting?

thanks everyone
ckielstra



Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands

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PostPosted: Thu Sep 20, 2012 4:57 am     Reply with quote

SCL should be working. Did you make your own hardware board or buy a ready made one?
Check physical connections, solder problems, etc.
PIC pin 14 (RC3 / SCL) is connected to what parts / pin numbers on your board?
With another program, can you make a LED blink on this port?

Code:
#define ADXL345_ADDR_WRITE     0xA6
#define ADXL345_ADDR_READ     0xA7
This seems suspicious to me. Where do these values come from?
lloureiro



Joined: 19 Sep 2012
Posts: 9

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PostPosted: Thu Sep 20, 2012 5:53 am     Reply with quote

Hello ckielstra

i purchased one made on sparkfun:

Triple Axis Accelerometer Breakout - ADXL345
https://www.sparkfun.com/products/9836

It is connected to pin 14 of adxl345.

The problem is that i don't see activity on pin pic, so i will follow your idea and make a led blink, to check if pin isn't damaged.

theses values are wrong :( it was to i2c program sorry :(

so...i have a question when i look to example "9356SPI.C" of ccs compiler:

Code:
 
   spi_write(0xa);
   spi_write(address);
   spi_write(data);


looking to adxl345, i need to write tree times? or two?
temtronic



Joined: 01 Jul 2010
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PostPosted: Thu Sep 20, 2012 6:20 am     Reply with quote

hmm....back to basics..

You ARE running this PIC and module on 3 volts right ??????
lloureiro



Joined: 19 Sep 2012
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PostPosted: Thu Sep 20, 2012 6:33 am     Reply with quote

Right not exactly 3v, but 3.3V
ckielstra



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PostPosted: Thu Sep 20, 2012 12:49 pm     Reply with quote

3.3V is fine for both the ADXL345 and PIC16F886.

I suggest you have a look at the Sparkfun site again as several code examples are posted there. For example this Arduino code example is easy to convert to CCS and should get you going.

Try this code and when not working come back here and post your complete program, that is, not using any special header files that are not included with the compiler ("../h/ring.h" )
lloureiro



Joined: 19 Sep 2012
Posts: 9

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3 wire vs 4 wire
PostPosted: Fri Sep 21, 2012 2:38 am     Reply with quote

Good morning.

I'm a little confused now. I saw that pic16f886 supports 3 wire spi.

http://ww1.microchip.com/downloads/en/DeviceDoc/41291D.pdf

But when I look at mssp diagram, it have SDO and SDI pins, not the same.

I only connect sda adxl345 to sda RC4/SDI/SDA of pic?
and the clock and chip select?

And I need change trisc direction, right?

Thanks
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Fri Sep 21, 2012 2:24 pm     Reply with quote

You also have SCL. Pin C3.

You can use _any_ pin to control CS. It is not a hardware 'feature' of the SPI interface. The interface has:

CLOCK - SCL
DATA OUT - SDO - must connect to the input of the other device
DATA IN - SDI - must connect to the output of the other device

Then CS on the slave device _you_ enable, by connecting to a pin on the PIC, and driving this LOW when you want to talk to the device, and raising it when the transaction has finished.

The fact that this is any pin, is why you can control more than one device, just using different pins to drive their CS lines.

No, you do not have to control TRIS. The compiler does this for you.

Best Wishes
bkamen



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PostPosted: Fri Sep 21, 2012 10:16 pm     Reply with quote

There's another convention for naming SPI lines for the data pins that give more "instant understanding" when looking at schematics and such..


MOSI - Master Out Slave In
MISO - Master In Slave Out


Just thought I'd mention...

-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D
FvM



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PostPosted: Sat Sep 22, 2012 2:58 am     Reply with quote

At first sight, there are two problems in your code:

- you are setting port C to all output after setup_spi(). This will reprogram SDI (=MISO) to an output and block SPI data read.
- you are not activating PIN_C0 during initialization

As mentioned by Ttelmah, setup_spi() takes care of the TRIS settings of SPI related pins, but it won't correct later changes to TRIS_C.

The SCK output is however supposed to work. If you don't see it, this point should be clarified first. Maybe it's shorted in hardware.
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