topic SPI always reads zero??? in Kinetis Microcontrollers

SPI always reads zero???

jonathanscott — Fri, 20 Jun 2014 14:04:56 GMT

Well, this is somewhat embarrassing, but I'm finally frustrated enough to ask for help. I have a simple routine to read 3 bytes from the SPI. It worked just fine through months of development, and then something changed, and now it always returns zeros despite the correct data clearly present on a scope (screenshots attached). This is an MK10DX128VMP5, using the IAR tools, with the SPI routines and drivers generated by PE. What I should get is statbyte[0] = 0x40, statbyte[1] = 0x00, and statbyte[2] = 0x0B, but instead they are all 0x00.

MYSPI_ClearRxBuf();

STROBE_MISO_PutVal(1); //strobe is done with GPIO pins

STROBE_MISO_PutVal(0);

for(i=0; i<3; i++){

MYSPI_SendChar(0x00); //clock in a char

spibyte = MYSPI_RecvChar(&statbyte[i]); //get it

}

STROBE_MISO_PutVal(0);

Does anybody know what's going on? I also attached a screenshot showing the spi configuration registers.

Thank you!!!

Re: SPI always reads zero???

mjbcswitzerland — Fri, 20 Jun 2014 23:47:57 GMT

Have you maybe overwritten the SPI-RX input pin configuration so that it doesn't see the data?

Regards

Mark

Re: SPI always reads zero???

jonathanscott — Mon, 23 Jun 2014 15:20:45 GMT

Good thought, Mark, but the pin configuration appears to be correct. I made some other changes, and now it's magically working again. I'll repost if it happens again.

Thanks,

Jonathan

Re: SPI always reads zero???

M_Grillo — Wed, 12 Nov 2014 13:40:11 GMT

Hello,

I'm having the same issue. What did you change to get MISO to work and not always report 0's? I'm using a K60D100 TWR board and trying to get SPI2 to work on PORTB(pins 20-23). Tried every example but no luck. MOSI, ,CLK and CS work fine.

Pin setup:

As a sanity check a tried grounding SIN (0x00..) and then tried tying SIN to 3.3V (0xffff...) Still read all 0's.

/* Configure PINs */

PORTB_PCR20 = (0|PORT_PCR_MUX(2)); //0x200; // Alt2 //CS

PORTB_PCR21 = (0|PORT_PCR_MUX(2)); //0x200; // Alt2 //CLK

PORTB_PCR22 = (0|PORT_PCR_MUX(2)); //0x200; // Alt2 //SOUT

PORTB_PCR23 = (0|PORT_PCR_MUX(2)); //0x200; // Alt2 //SIN

Using MQX 4.1.1 w/DMA on SPI2

Thanks,

Mark