SPI receive data from slave trouble

[Anonymous]

I'm new to SPI and have run into a snag. I have a a PCB with a PSoC 3 trying to communicate to an nRF24L01+. With PsoC Creator, I have added an SPI mater to the project and have a simple loop where, after I do a "SPIM_Start()" I try to do some simple register write/read on the slave. I have a logic analyzer showing me the SPI data that is being transfered. It appears as though my write to say register 0 is working .. I basically do a "SPIM_WrtieTxData(<addr>+32)"  ( register write requires bit 6 to be a "1" to indicate a register write, so register "0" if the value == 32), then I do another SPIM_WrtieTxData(<value>) to write the data to that register. So far so good, and the analyzer shows the xfer. But, when I try to read the register; I send "SPIM_WrtieTxData(<addr>)" (bit 6 is clear for a read, so just the reg addr is needed) then another write ("SPIM_WrtieTxData(0xFF)") with bugus data, which gives the slave the clock cycles it needs to shift the return value out  (verified with analyzer), I then do a "temp = SPIM_ReadRxData()" to read what I would think would be the slave return data but the value returned is NOT what is expected (nor what the analyzer shows). So, I must be missing some simple step before I should read the slave data.

Here is a simple example of my code.. and a snapshot of the analyzer output (attached)

My guess is I'm missing some Tx and/or Rx status checks but I'm not sure what and why?

Any suggestions?

main() {

  uint8 addr, val;

  SPIM_Start();

  for (;;) {

     addr = 32;     // Set bit 6 to write to a register (i.e.  001a aaaa ..  "aaaaa" is the register address). So reg "0" here.

      SPIM_WriteTxData(addr);   // Tx addr to slave device

      SPIM_WriteTxData(0x1E);  // Write 0x1E (to register 0 .. just an xfer test, not tryiing to set anything, yet).

      CyDelayUs(10u);   // Give small delay for the xfer

     addr = 0;                    // Now read regsiter 0. A read operation is just the address (i.e. 000a aaaa)

     SPIM_WriteTxData(addr);     // Tx addr to slave

     SPIM_WriteTxData(0xFF);    // Tx bogus data to give slave the clock cycles it needs to shift out register 0 contents

     CyDelayUs(10u);   // Give small delay for the xfer

     val = SPIM_ReadRxData();     // We should see 0x1E, but we val == 0x00 (analyzer shows 0x1E).

  }

}

[AnkitaS_51]

Please post the project

[Anonymous]

Here is my "main.c" (attached). If you need to whole project let me know.

There is nothing special about this code, all I'm trying to do is get SPI write/reads to/from an nRF24L01+ to work. Since my original post, I have added a loop that waits for SPIM_ReadRxStatus(). This seems to have fixed the issue I was having and now see a return value when reading SPIM_ReadRxData(). But, if you could quickly look at the code and make suggestions, since I'm still not really sure I'm doing things correctly, I would greatly appreciate it.

[AnkitaS_51 · Accepted solution]

Can you please  check this Code Example  named as "SPI_Design" .You will get this Code example by going to this tab as shown in image attached in Creator-

It may be helpful