Part Number:TIDC-CC2650STK-SENSORTAG
Tool/software: TI-RTOS
Using SPI on the CC2650STK. Multiple devices are hooked to the SPI_0 bus - the on board flash, an external sensor and an SD card. The first two work fine, but accessing the SD card produces a lot of difficulties. While my code runs smoothly on a little 16bitter in a FPGA (using GP I/O pins), it performs unreliably and with lots of errors with the SensorTag/RTOS SPI/µDMA engine. Main cause seem to be long time gaps between the singular SPI transactions. Unfortunately for SD card you have to poll the bus after sending a command. So for each single poll byte I have to launch a transaction. - Questions:
- Is there any way to have the SPI engine continuously clocking in bytes until a certain pattern arrives?
- What causes the long pauses between transactions and - how? - can they be cut? Possibly the RTOS does a lot of stuff here that I do not need. F.i. I have no power saving needs.
Below are two scope shots illustrating the problem. Bus speeds are comparable - 400 kbps on the SensorTag.
This is the FPGA soft core. No gaps between singular bytes, nor betwen writing/readi
This is the same command sequence on the SensorTag.Thank you in advance for helping!