SPI help

[ckielstra]

[das]

I will try that. Right now, here is the current code:

#int_RDA
#define SPI_MODE_0_0 (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_0_1 (SPI_L_TO_H)
#define SPI_MODE_1_0 (SPI_H_TO_L)
#define SPI_MODE_1_1 (SPI_H_TO_L | SPI_XMIT_L_TO_H)

int byte1, byte2, byte3, byte4;
int byte_1, byte_2, byte_3, byte_4;
int32 value;
int i;
int completed, loop;



RDA_isr()
{
puts("RDA was tripped");
}



void main()
{
int loop = 1;
OUTPUT_HIGH(PIN_D0); //Start with CS high

setup_spi(SPI_MASTER | SPI_MODE_0_0 | SPI_CLK_DIV_4 );

delay_ms(5000); //Delay 5 seconds
puts("Magnum Torque Meter Initialized");
while(TRUE)
{
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
loop = 1;
OUTPUT_LOW(PIN_D0); //Start the conversion
delay_ms(10); //Delay 10 ms for the conversion to complete
do //Do...while loop
{
if(input(PIN_C4) == 0) //Check to see if the conversion is completed
{
byte_4 = spi_read(byte4);
byte_3 = spi_read(byte3);
byte_2 = spi_read(byte2);
byte_1 = spi_read(byte1);

value = make32(byte_4, byte_3, byte_2, byte_1);
for(i = 0; i < 32; i++)
{
putc(bit_test(value, 31 - i));
}
OUTPUT_HIGH(PIN_D0);
completed = 1;
}

if(input(PIN_C4) == 1)
{
delay_us(1);
} //Closing if PIN_
}while(loop = 1);
delay_ms(10000);
}
}

[ckielstra]

Some general remarks:
- When posting code on this forum please use the 'code' buttons. It will help to preserve the layout of your program and makes it easier for us to read the code.
- When debugging a problem like this, get rid of all other program code that might interfere. Especially enabled interrupts might cause unexpected side effects.
- Never use a printf or put instruction in an interrupt handler unless you know and accept the side effects. Receiving a character on the UART will take the same amount of time as sending a single character. You are receiving one character and transmitting 10-fold, this will block receiving and cause buffer overflow. The UART will stop responding at receive buffer overflow (the third character). Resetting the UART requires specific actions or adding the ERRORS directive to the #use RS232 directive.


Then about your program:
- Move the enable_interrupt() functions out of the while loop. You never disable these functions, so why add the overhead?
- I made a mistake in an earlier post. For the spi_read() to generate a clock signal you have to pass the spi_read() function a value, however this doesn't have to be a variable. Just any constant value will do for generating the clock signal, for example spi_read(0).
- while(loop = 1); Change this to '=='
- In SPI-mode 0,0 you are supposed to read 3 bytes, not 4.
- You said you want to operate in single conversion mode. If so, then your handling of the ChipSelect line seems incorrect (read Ttelmah's note on this).

[das]

I refined some of the code shown above - and made changes to keep it in constant conversion mode. I am still seeing all outputs as zeros. Any other ideas? Current code is:

#int_RDA
#define SPI_MODE_0_0 (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_0_1 (SPI_L_TO_H)
#define SPI_MODE_1_0 (SPI_H_TO_L)
#define SPI_MODE_1_1 (SPI_H_TO_L | SPI_XMIT_L_TO_H)

int byte1, byte2, byte3, byte4;
int byte_1, byte_2, byte_3, byte_4;
int32 value;
int i;
int completed, loop;



RDA_isr()
{
puts("RDA was tripped");
}



void main()
{
int loop = 1;
OUTPUT_LOW(PIN_D0); //Start with CS high

setup_spi(SPI_MASTER | SPI_MODE_0_0 | SPI_CLK_DIV_4 );

delay_ms(5000); //Delay 5 seconds
puts("Initialized"); //Output string for debug
while(TRUE)
{
enable_interrupts(INT_RDA);
enable_interrupts(GLOBAL);
loop = 1;
delay_ms(10); //Delay 10 ms for the conversion to complete
do //Do...while loop
{
if(input(PIN_C4) == 0) //Check to see if the conversion is completed
{
byte_4 = spi_read(byte4);
byte_3 = spi_read(byte3);
byte_2 = spi_read(byte2);
byte_1 = spi_read(byte1);

value = make32(byte_4, byte_3, byte_2, byte_1);
for(i = 0; i < 32; i++)
{
putc(bit_test(value, 31 - i) + 48);
}
putc(10);
putc(13);
loop = 0;
}

if(input(PIN_C4) == 1)
{
delay_us(1);
}
delay_ms(10000);
}while(loop = 1);
}
}

I know that you said in a previous response something about the
if(input(PIN_C4) == 0)

Can you elaborate?

[Ttelmah]

Your code, now generates 32 clocks. This won't work.
You need to either generate 25 clocks, and not operate the CS, or generate 24 and operate the CS.
Generating 32 clocks, will result in the bytes being shifted, and a garbage result.
The way to generate the extra clock, is to simply toggle it in software.

[das]

Sorry - I didn't realize about the code posting. I disabled what you recommended. Looking at the Mode 0 0 it generates 4 bytes - not three based on the Figure 5-7. That would seem to work better for the continuos conversion anyway as it will send out the 25th clock cycle.

[ckielstra]

[das]

Thank you for the help. I am having some issues compiling the low level changes in. I am getting errors on your recommendation. Do these need another specification?

[ckielstra]

What is the version number of your compiler?

[ckielstra]

A problem in your program is that you are trying to read the _RDY signal from PIN_C4. This will return undefined values as the pin is used by the SPI module.
Not tested, but could you give the following program a try?

[Ttelmah]

PIN C4, should read OK.
If you look at the 'logic' for the I/O pin, there is a pickoff for read, and a picoff for the SPI, and both should be working. When SPI is enabled, it overrides the logic feeding the 'output' connections, but doesn't affect the input connections in this case.
I have driven the ADC involved here OK, but have only used it in single conversion mode, not continuous conversion mode.
I used a pull up on the SD line, and read PIN C4 fine.

Best Wishes

[Ttelmah]

I think there is a critical misnderstanding about the useable 'modes' going on here.
If you use the four byte transfer, you cannot read C4, to get the RDY status. When four byte transfer is used, the RDY bit is transferred as the first _bit_ of the fourth byte, and from then he line sits high. To have the bit available to read on pin C4, you need to use the 25bit transfer mode.

Best Wishes

[ckielstra]

[das]

I can change it to single conversion mode... I just need it to work ASAP. Can I see your code that you used to drive it in single conversion mode?

[Ttelmah]

The more I read this part of the sheet, the more I am inclined to go back to my original statement, that you cannot (sensibly) use the 4 byte mode, for continuous conversions!.
The diagram that shows the status in the first bit, is from a mode with CS enabled, where the bit becomes available when CS is lowered, and is then clocked in as the first bit of the first byte. The description text for the two wire transfer (without CS), says that the RDY line activates one clock after 24 bits are transferred, and a transfer cannot be interrupted. As such then, four byte mode cannot be used this way. Look at paragraph 5.4.1. It is the only one that refers to the mode being used, and makes no mention of using a four byte transfer.

Best Wishes