CC3235MODSF: SPI reads incorrect data

Robert James

Part Number: CC3235MODSF

Hi,

I am trying to interface the KX134 to the CC3235MODSF Launchpad. I am able to send and receive one byte of data successfully.

I am getting incorrect data while reading 7 bytes. I am getting the incorrect value FF in the 3rd and 5th bytes.

SPI Code

SPI_Handle masterSpi;
SPI_Params spiParams;
SPI_Params_init(&spiParams);
spiParams.frameFormat = SPI_POL0_PHA0;
spiParams.bitRate = 250000;
spiParams.dataSize = 8;
spiParams.transferCallbackFxn = NULL;
spiParams.transferMode = SPI_MODE_BLOCKING;
masterSpi = SPI_open(CONFIG_SPI_MASTER, &spiParams);

transmitBuffer[0] = 0x88;
transmitBuffer[1] = 0x00;
transmitBuffer[2] = 0x00;
transmitBuffer[3] = 0x00;
transmitBuffer[4] = 0x00;
transmitBuffer[5] = 0x00;
transmitBuffer[6] = 0x00;
transaction.txBuf =(void *)transmitBuffer;
transaction.rxBuf = (void *)receiveBuffer;
transaction.count = 7;
SPI_transfer(masterSpi, &transaction);

I have compare data packets between Arduino and CC3235

SPI Read Working one (Arduino):

SPI not working one (CC3235)

I see MOSI pin send 0x00 values and never go to a high state between zeros like Arduino.

Could you please help me to fix this issue.

Regards,

Robert

over 2 years ago

0 Shlomi Itzhak over 2 years ago

TI__Guru 62515 points

Thanks for the post, an expert will look into it and reply back as soon as possible.

Shlomi

0 Kobi Leibovitch over 2 years ago in reply to Shlomi Itzhak

TI__Guru 63006 points

Please go through our hardware review:

https://www.ti.com/tool/SIMPLELINK-WIFI-DESIGN-REVIEWS

0 Robert James over 2 years ago in reply to Kobi Leibovitch

Prodigy 60 points

Hi Kobi,

Thanks for the reply. I'm having the same problem as the poster below.

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1017315/tms320f28379d-spi-mosi-idle-state-condition

I have added 5k pull-down resistor to MOSI pin, but it didn't work.

I have used the development board and connected pins like below using the breadboard wires.

CC3235MOD Launchpad - KX134 dev board

P08 (CS) ==========> CS

P05 (SLK) ==========> SCLK

P06 (MISO) ==========> SDO

P07 (MOSI) ==========> SDI

Please let me know your suggestion.

Regards,

Robert

0 Dylan Hubbard over 2 years ago in reply to Robert James

TI__Mastermind 45185 points

Hey Robert,

Its very likely there are pull-ups somewhere on the Arduino board since the signals go high during the idle states when I expect the I/O to be tri-stated. I don't really understand the intention of the pull-down on MOSI nor do I see how the High states in between bytes makes a difference for the communication. The logic analyzer even decodes them the same. To me it just looks like slave device is sending back completely different data.

When using jumper wires on digital signals, its possible to have signal integrity issues from the added inductance. It may be good to look at this piece of communication with an oscilloscope.

0 Robert James over 2 years ago in reply to Dylan Hubbard

Prodigy 60 points

Hi Dylan,

Your right. SPI is sending the correct data. I did not convert the 2's complement value.

Issue is resolved. Thank you so much for the input.

Regards,

Robert

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CC3235MODSF: SPI reads incorrect data