CCS/CC2640: lower CC2640 SPI clock

You can change the bitRate to anything lower than 4M(slave)/12M(master).

When you use our SPI driver which comes with TI-RTOS, you can easily set the bit rate by changing the bitRate field in the initialization step

 *  PIN_Handle pinHandle;
 *  SPI_Handle handle;
 *  SPI_Params params;
 *  SPI_Transaction transaction;
 *  uint8_t txBuf[] = "Heartbeat";    // Transmit buffer
 *  uint8_t rxBuf[9];                 // Receive buffer
 *  PIN_Id misoPinId;
 *  uint32_t standbyDurationMs = 100;
 *
 *  // Init SPI and specify non-default parameters
 *  SPI_Params_init(&params);
 *  params.bitRate     = 1000000; // use whatever you want as long as it's within the spec
 *  params.frameFormat = SPI_POL1_PHA1;
 *  params.mode        = SPI_MASTER;
 *
 *  // Configure the transaction
 *  transaction.count = sizeof(txBuf);
 *  transaction.txBuf = txBuf;
 *  transaction.rxBuf = rxBuf;

Hi Eirik

for the first thread won't apply to out case, we don't implement external crystal on our board. we have to use internal 512K clock. 

the second thread of 1792301 is a bit too complicate for me to read through, may repeat my question again. I am using ADS1292 with internal clock 512K. 

MCU us cc2640. when we use SPI to  communication with ADS1292, we notice the clock is higher than the ADS1292 data sheet requirement, internal clock only support upto 1Mhz SPI clock.

if the thread you mentioned in /1792301 is explain how to make this work with internal 512K clock situation. then I will sit down and spend some to read this link line by line. 

Thanks,

David Sun

Hello David,
The general SPI rate on ADS1292 is limited to maximum 20 MHz:
tSCLK - SCLK period 50 66.6 ns

There are other considerations and rules outlines in the data sheet which you will have to study carefully to make it work. For example at which speed the SPI interface can run during a register read or write (SCLK can be only twice the speed of fCLK, therefore use the balanced option of 1.1 MHz in sensor controller studio). It is worth reading the threads i posted links to above in case you find some useful info.

Hi Eirik

in one of the thread you mentioned. I copied here to make it easier to reference. we are using internal clock of ads1292. so the max PCI clock is 512kHz, if I understand correctly. but the sensor controller minimus clock for SPI is 1.1Mhz.  is it possible to use sensor controller to drive ADS 1292 SPI clock? 

Yes or NO, Please.

David

Hello Simon,
Can you show the waveforms?
Did you configure the ads1292 for using external clock at 2 MHz? I don't think the internal clock on the ads1292 support more than 512 kHz for the SPI clock:

"SCLK can only be twice the speed of fCLK during register reads and writes. For faster SPI interface, use fCLK = 2.048 MHz and set the CLK_DIV register bit (in the LOFF_STAT register) to '1'.

www.ti.com/.../ads1292.pdf

Best Regards, Eirik