Receiving SPI data through DMA - STM32 internal hardware error ?

kn7 · ‎2011-01-10

Posted on January 10, 2011 at 22:55

#spi-dma

Tesla DeLorean · ‎2011-05-17

Posted on May 17, 2011 at 14:21

Try doing it slower. Try using different source/dest buffers. Look at the transaction with a logic analyzer.

Tips, Buy me a coffee, or three.. PayPal Venmo
Up vote any posts that you find helpful, it shows what's working..

kn7 · ‎2011-05-17

Posted on May 17, 2011 at 14:21

I set the slowest SPI clock possible which is below 400 kHz in my application. It

didn't help. I will try to use different buffers.

kn7 · ‎2011-05-17

Posted on May 17, 2011 at 14:21

I've just checked different buffers as well as setting 16-bit SPI data length. It didn't help either. I don't have a logic analyzer...

I also examined my SPI functions on 2 different PCBs with 2 different SD cards and the problem existed with the two cards and PCBs.

lowpowermcu · ‎2011-05-17

Posted on May 17, 2011 at 14:21

Hi k.robert,

Just one question:

Why channel 2 and channel 3 have the same address, I guess that one should have buffer address and the other the SPI data register address, isn't it ?

DMA1_Channel2->CMAR = (u32) Buffer;

DMA1_Channel3->CMAR = (u32) Buffer;

The code isn't commented si it needs much time to understand.

MCU Lüfter

lowpowermcu · ‎2011-05-17

Posted on May 17, 2011 at 14:21

Hi Robert,

I think that it should be something like this

DMA1_Channel2->CPAR = (u32) SPI_ADDRESS;

or

DMA1_Channel3->CPAR = (u32) SPI_ADDRESS;

Thanks to correct me in any case.

MCU Lüfter

kn7 · ‎2011-05-17

Posted on May 17, 2011 at 14:21

The following code:

DMA1_Channel2->CPAR = (u32) SPI_ADDRESS;

or

DMA1_Channel3->CPAR = (u32) SPI_ADDRESS;

is written in DMA initialization routine. SPI_ADDRESS equeals to SPI data register address (SPI_DR)

To receive data via SPI the CLK clock must be active. The only way to do so is to send ''dummy'' data like it is done by sending data through SPI.

I discovered something strange. It turns out that sending data sometimes works incorrectly as well... I connected an oscilloscope to CLK and MOSI. The CLK signal is ok but i noticed there are corrupted bits sent on MOSI (instead of '1' i get '0' in some of the sent bytes). For example, when i send all bytes of 0x18 value, some of the bytes that i see on the oscilloscope are 0x00.

lowpowermcu · ‎2011-05-17

Posted on May 17, 2011 at 14:21

Hi robert,

In such case, you should check your board, perhaps you have something pulling down the line.

MCU Lüfter

kn7 · ‎2011-05-17

Posted on May 17, 2011 at 14:21

It seems i solved the problem with sending data. The data length in SPI register (DFF bit) was set to 16-bit wide. In such case DMA->CMAR memory address register should be written with a value which must be an even numer (2 byte aligned). If the addres is not even DMA reads incorrect values which in turn are sent through SPI. I set the correct address and it work fine now. But i still have issues with the receiver...

nanayakkaraan · ‎2011-05-17

Posted on May 17, 2011 at 14:21

Hello Robert,

Can you please mention the steps you have taken in order to get the receiving part of SPI work without DMA. I am also trying to do that. But it is not working properly.

I need to receive in slave mode.

Thank you.