RTOS/CC2640: Using SPI for basic byte transfers

Thanks so much, I believe I have it working now. Two follow up questions:

1) Currently in CC240R2_LAUNCHXL.h I have:

#define CC2640R2_LAUNCHXL_SPIO_MISO            IOID_8
#define CC2640R2_LAUNCHXL_SPIO_MOSI            IOID_9
#define CC2640R2_LAUNCHXL_SPIO_CLK              IOID_10
#define CC2640R2_LAUNCHXL_SPIO_CSN             PIN_UNASSIGNED

When I try to change MISO to IOID_14, MOSI to IOID_15, CLK to IOID_16 and CSN to IOID_26, the SPI fails. Is there a reason one has to use specific pins (or couldn't use the pins I want to)?

2) I've written a short script to send the bytes 0x0B and 0x0E which appears to work, but almost every time I run it, the 7th clock cycle on the 2nd byte is distorted. Is that something to worry about? Normally I would assume just a poor connection or trigger or something, but it's always the same part that seems to be truncated early. I've attached a scope readout for reference:

Thanks!

Hello,

1. It could be because IOID_14 is being used by the PIN init table for BTN1. Try commenting out this line and adding the SPI0_CSN line to the table.

2. This could be caused by a poor connection or maybe the scope. Is the behavior of the sesnor still good or are you having problems when trying to send commands?

Regards,
AB

Hi AB,

1. This issue is definitely with IOID_14 as the other PINS I can change and still succesfully transmit. I made the changes above (see blow) but am still having problems. Could it be something with how that PIN is directly wired to the Button on the launchpad?



2. I'm having trouble connecting with the sensor, but I'm not sure the issue is with the launchpad. The goal of my script (for now) is to send three bytes (0x0A, 0x1F, 0x52), and then send two more bytes (0x0B, 0x2D) and read in one byte. According to my oscilloscope that's exactly what is sent, but MISO line stay low the whole time which makes me think its an issue with the chip (or what I'm saying to it) rather than the script itself.

Thanks
Reed


/* SPI Board */
#define CC2640R2_LAUNCHXL_SPI0_MISO IOID_14 //8 /* RF1.20 */
#define CC2640R2_LAUNCHXL_SPI0_MOSI IOID_15 //9 /* RF1.18 */
#define CC2640R2_LAUNCHXL_SPI0_CLK IOID_16 //10 /* RF1.16 */
#define CC2640R2_LAUNCHXL_SPI0_CSN IOID_26 //PIN_UNASSIGNED

/* Discrete Inputs */
#define CC2640R2_LAUNCHXL_PIN_BTN1 IOID_13
//#define CC2640R2_LAUNCHXL_PIN_BTN2 IOID_14

const PIN_Config BoardGpioInitTable[] = {

CC2640R2_LAUNCHXL_PIN_RLED | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW | PIN_PUSHPULL | PIN_DRVSTR_MAX, /* LED initially off */
CC2640R2_LAUNCHXL_PIN_GLED | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW | PIN_PUSHPULL | PIN_DRVSTR_MAX, /* LED initially off */
CC2640R2_LAUNCHXL_PIN_BTN1 | PIN_INPUT_EN | PIN_PULLUP | PIN_IRQ_BOTHEDGES | PIN_HYSTERESIS, /* Button is active low */
CC2640R2_LAUNCHXL_SPI0_MISO | PIN_INPUT_EN | PIN_PULLUP | PIN_IRQ_BOTHEDGES | PIN_HYSTERESIS, /* Button is active low */
CC2640R2_LAUNCHXL_SPI_FLASH_CS | PIN_GPIO_OUTPUT_EN | PIN_GPIO_HIGH | PIN_PUSHPULL | PIN_DRVSTR_MIN, /* External select */
CC2640R2_LAUNCHXL_UART_RX | PIN_INPUT_EN | PIN_PULLDOWN, /* UART RX via debugger back channel */
CC2640R2_LAUNCHXL_UART_TX | PIN_GPIO_OUTPUT_EN | PIN_GPIO_HIGH | PIN_PUSHPULL, /*
CC2640R2_LAUNCHXL_SPI0_MOSI | PIN_INPUT_EN | PIN_PULLDOWN, /* SPI master out - slave in */
CC2640R2_LAUNCHXL_SPI0_MISO | PIN_INPUT_EN | PIN_PULLDOWN, /* SPI master in - slave out */
CC2640R2_LAUNCHXL_SPI0_CLK | PIN_INPUT_EN | PIN_PULLDOWN, /* SPI clock */

PIN_TERMINATE
};

Hi AB,

Changing to PIN_UNASSIGNED seems to fix the problem. I am still very stumped by no data from MISO.

I've connected the ADXL sensor to an arduino and run sample code which shows the sensor works and has fine connections. Comparing the Oscilloscope readings from the Arduino to the Launchpad show a couple basic differences. The first Difference is the Chip Select in the arduino goes low earlier than the launchpad and stay low for the length of the transfer (compared to going high between bytes). The second difference is for the arduino, MOSI is default high.

I suspect the issue is with Chip Select rather than MOSI, as MOSI still goes low in time for the first rising edge of the clock. For Chip Select, I also tried implementing a software CS, where a pin manually was set low before the transfer and then pulled back high but that didn't seem to fix anything (Though CS was low a long time before the clck started). In addition I disconnected MISO from the launchpad and connected it straight to the scope so as to test for and error in the sensor being able to pull the PIN high/low but that seemed to have no effect.

Thanks

Reed

Successful Arduino Transfer (triggered on Clock, so CS is not shown going low)

Launchpad - Hardware CS

Launchpad - Software CS

Hello,

the reason for the MOSI pin going HIGH between transmission on the Arduino and not on our device is because you have the pin setup with a pull down(I do not think this the problem either as the sensor's datasheet states that the MOSI pin is a 'Don't Care' when it is not transmitting):

CC2640R2_LAUNCHXL_SPI0_MOSI | PIN_INPUT_EN | PIN_PULLDOWN, /* SPI master out - slave in */
CC2640R2_LAUNCHXL_SPI0_MISO | PIN_INPUT_EN | PIN_PULLDOWN, /* SPI master in - slave out */
CC2640R2_LAUNCHXL_SPI0_CLK | PIN_INPUT_EN | PIN_PULLDOWN, /* SPI clock */

You can try making it a pull up and see if this fixes the issue.

You can make CS pin SW controlled and make sure you pull it down before you start a transmission by putting a delay in between transfer and pulling it down. According to the ADXL datasheet the time you need is atleast 100ns.

Regards,
AB

In BoardGPIOInitTable[] I've set:

CC2640R2_LAUNCHXL_SPI0_MOSI | PIN_INPUT_EN | PIN_PULLUP

but that didn't seem to do anything. I also added a SW CS pin.

New Scope:

For reference, here is my code. I doubt the issue is with MOSI being default low, but any suggestions on how to make it default high would be appreciated

/* XDC Module Headers */
#include <xdc/std.h>
#include <xdc/runtime/System.h>

/* BIOS Module Headers */
#include <ti/sysbios/BIOS.h>
#include <ti/drivers/GPIO.h>
#include <ti/drivers/SPI.h>

/* Example/Board Header files */
#include "Board.h"

#include <stdint.h>
#include <stddef.h>
#include <stdio.h>
#include <ti/drivers/PIN.h>

/*
 *  ======== main ========
 */
int main()
{
    int MSGSIZE = 3;
    SPI_Handle      spi;
    SPI_Params      spiParams;
    SPI_Transaction spiTransaction;
    uint8_t         transmitBuffer[MSGSIZE];
    uint8_t         recieveBuffer[MSGSIZE];
    bool            transferOK = FALSE;

    /* Call driver init functions */
    Board_initGeneral();
    ledPinHandle = PIN_open(&ledPinState, spipins);

    SPI_init();
    SPI_Params_init(&spiParams);
    spiParams.dataSize = 8;
    spiParams.bitRate = 4000000;
    spiParams.mode = SPI_MASTER;
 

    spi = SPI_open(Board_SPI0, &spiParams);
    if (spi == NULL){
        printf("SPI_open failed!\n");
    }

    transmitBuffer[0] = 0x0A;
    transmitBuffer[1] = 0x1F;
    transmitBuffer[2] = 0x52;

    spiTransaction.count = MSGSIZE;
    spiTransaction.txBuf = transmitBuffer;
    spiTransaction.rxBuf = recieveBuffer;

    transferOK = SPI_transfer(spi, &spiTransaction);
    if (!transferOK) {
        printf("Error in SPI_transfer1!\n");
    }

    BIOS_exit(0);  /* terminates program and dumps SysMin output */
    return(0);
}




const PIN_Config BoardGpioInitTable[] = {

    CC2640R2_LAUNCHXL_PIN_RLED | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW | PIN_PUSHPULL | PIN_DRVSTR_MAX,       /* LED initially off */
    CC2640R2_LAUNCHXL_PIN_GLED | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW | PIN_PUSHPULL | PIN_DRVSTR_MAX,       /* LED initially off */
    CC2640R2_LAUNCHXL_PIN_BTN1 | PIN_INPUT_EN | PIN_PULLUP | PIN_IRQ_BOTHEDGES | PIN_HYSTERESIS,          /* Button is active low */
    //CC2640R2_LAUNCHXL_PIN_BTN2 | PIN_INPUT_EN | PIN_PULLUP | PIN_IRQ_BOTHEDGES | PIN_HYSTERESIS,          /* Button is active low */
    CC2640R2_LAUNCHXL_SPI_FLASH_CS | PIN_GPIO_OUTPUT_EN | PIN_GPIO_HIGH | PIN_PUSHPULL | PIN_DRVSTR_MIN,  /* External flash chip select */
    CC2640R2_LAUNCHXL_UART_RX | PIN_INPUT_EN | PIN_PULLDOWN,                                              /* UART RX via debugger back channel */
    CC2640R2_LAUNCHXL_UART_TX | PIN_GPIO_OUTPUT_EN | PIN_GPIO_HIGH | PIN_PUSHPULL,                        /* UART TX via debugger back channel */
    CC2640R2_LAUNCHXL_SPI0_MOSI | PIN_INPUT_EN | PIN_PULLUP,                                            /* SPI master out - slave in */
    CC2640R2_LAUNCHXL_SPI0_MISO | PIN_INPUT_EN | PIN_PULLDOWN,                                            /* SPI master in - slave out */
    CC2640R2_LAUNCHXL_SPI0_CLK | PIN_INPUT_EN | PIN_PULLDOWN,                                             /* SPI clock */
    CC2640R2_LAUNCHXL_SPI0_CSN | PIN_INPUT_EN | PIN_PULLDOWN,

    PIN_TERMINATE
};

I think the PIN_Config Table is overridden in SPI_Open by the call to SPI_initIO(). Looking there, I see code for configuring the MOSI:

else {
/* Configure IOs for master mode */
spiPinTable[i++] = hwAttrs->mosiPin | PIN_GPIO_EN | PIN_GPIO_LOW | PIN_PUSHPULL | PIN_INPUT_DIS | PIN_DRVSTR_MED;

but changing to PIN_GPIO_HIGH still has no effect