TMS320F28075: Interfacing MCP4921 DAC with tms320f28075 using SPI

Anvaya,

Did you ensure ensure that the GPIO group mux is configured properly? For GPIO22, GPAGMUX2 =1, GPAMUX2 = 2.
What hardware are you using? Is this a LaunchPad, ControlCard, or custom hardware? have you verified your HW is correct?
Please see my recent response on this thread regarding SPI operation: e2e.ti.com/.../689215 have you attempted to transfer any data yet? The SPI will not toggle the Clock until a data transmission is occurring.

Thanks,
Mark

Hi Mark,

Answers to your questions,

1) Yes, the mux is getting configured properly. I have verified register status of both GPAMUX2 and GPGAMUX2.

2) I am transferring a 16 bit data word after enabling the module. Mine is a custom hardware.

I am using SPI in non-FIFO mode and only for transmitting data .

And I am using chip select pin as normal GPIO pin and handling it through software only.

Here is the code I am using to initialize and transmit the data. I have used functions provided in driverlib of C2000 ware for 28075 controller. Please let me know what I am missing something or is it the right way to generate clock and transmit data.

I also want to know when does the SPIDAT register get loaded with SPITXBUF data. Because I observed that data comes in SPITXBUF but SPIDAT gets loaded with 0xffffffff.

I am also attaching snapshot of register status before and after run.

void spiInitDAC()

{

   /* Initialize device clock*/

   SysCtl_enablePeripheral(SYSCTL_PERIPH_CLK_SPIB);

   //clock    

   GPIO_setPinConfig(GPIO_22_SPICLKB);

   GPIO_setDirectionMode(22, GPIO_DIR_MODE_OUT);

   //SIMO

   GPIO_setPinConfig(GPIO_24_SPISIMOB);

   GPIO_setQualificationMode(24, GPIO_QUAL_ASYNC);

   //SOMI

   GPIO_setPinConfig(GPIO_25_SPISOMIB);

   GPIO_setPadConfig(25, GPIO_PIN_TYPE_PULLUP);

   GPIO_setQualificationMode(25, GPIO_QUAL_ASYNC);

   //chip select as GPIO pin only

   GPIO_setPadConfig(23, GPIO_PIN_TYPE_STD);

   GPIO_setDirectionMode(23, GPIO_DIR_MODE_OUT);

   GPIO_writePin(23,1);

   /* Must put SPI into reset before configuring it*/

   SPI_disableModule(SPIB_BASE);

   /*SPI configuration. Use a 1MHz SPICLK and 16-bit word size.*/

   SPI_setConfig(SPIB_BASE, DEVICE_LSPCLK_FREQ, SPI_PROT_POL0PHA0,

                 SPI_MODE_MASTER, 1000000, 16);

   /*Stop after 16 bit data transfer is complete*/

   SPI_setEmulationMode(SPIB_BASE, SPI_EMULATION_STOP_AFTER_TRANSMIT);

   /*Configuration complete. Enable the module.*/

   SPI_enableModule(SPIB_BASE);

}

void config_mcp4921()

{

  uint16_t write_command = {0x3C20};

  GPIO_writePin(23,0);

  SPI_writeDataNonBlocking(SPIB_BASE,write_command);

  GPIO_writePin(23,1);

}

Befor Run

After Run

Thanks,

Anvaya