SPI receives bad response from a SD card

[dax]

I ve a problem with the SPI interface. Im comunicating with a SD card and I can send to it data and comands and everything goes OK. But the bytes that the card sends to the pic are not correctly received.

for example when the card receives a command correctly it should send a byte of response with this value 00000001. The PIC never receives that value, it receives 10000000. Testing more commands I realised that what the PIC really does its to take the 7 more significative bits of the command and add a 1 as the MSB.

The line is high if nothings happens, so

111111111111000000111111111111 --> this is the correct byte
111111111111000000111111111111 -->the PIC takes that

My SPI configuration is

SETUP_SPI(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_4 | SPI_SS_DISABLED);

I use SPI_READ to receive the data.

So after thinking a lot I cannot see where is the problem, and why it do that, If somebody has any idea, all is welcome. Thanks a lot

[Ttelmah]

You will get exactly this effect if you are reading the SPI data on the wrong clock edge. There is a seperate configuration bit for Spi, to determine the clock edge to use for transmit, and to use for receive. You are only setting the transmit configuration bit. Try adding the 'SPI_SAMPLE_AT_END' configuration to your setup.

Best Wishes

[ckielstra]

[PCM programmer]

[dax]

Thanks a lot to everybody, you save me lot of time!

Ive solved my problem with the SPI_SAMPLE_AT_END and Ive also wrotten the more eficient library to manage the SPI.


thank you again!
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dax