Hello,
We use NRF52 and the SPI protocol to read the ADS7866. But we are facing a problem when reading at high speed, we want to make one read transaction of 2 Bytes every 5µs ( to achieve a 200KHz ADC )
Before explaining which method was used, there is the SPI configuration that we use:
#define NRF_DRV_SPI_CUSTOM_CONFIG \
{ \
.sck_pin = SPI_SCK_PIN, \
.mosi_pin = SPI_MOSI_PIN, \
.miso_pin = SPI_MISO_PIN, \
.ss_pin = SPI_ADC7866_PIN, \
.irq_priority = SPI_DEFAULT_CONFIG_IRQ_PRIORITY, \
.orc = 0xFF, \
.frequency = NRF_DRV_SPI_FREQ_4M, \
.mode = NRF_DRV_SPI_MODE_0, \
.bit_order = NRF_DRV_SPI_BIT_ORDER_MSB_FIRST, \
}
We have tried 3 different ways:
1: Make on bulk read of 100 Bytes using the SPI driver (`nrf_drv_spi_transfer()`). But it's does not work because, as you can see on the ADS7866 documentation, the CS signal should have a falling edge every 5µs to trigger the ADC acquisition.
2: Try to read 2 bytes per 2 bytes using the same driver but the best performance we can get is 7.3µs between each transaction ; this is too slow as we need 5µs.
3: Try to use an external clock as a CS to force the CS to fall edge every 5µs. But we failed to synchronize the SPI driver and this external clock.
What do you think about our problem ? In your opinion, what is the best way to do the job ?
