nRF8001 chip select pin

[MBlau]

Hi

I have a MCU with an external sensor connected via SPI sampling data at 1000Hz. Using the nRF8001 with REQN and RDYN lines is making trouble. The REQN line is pulled LOW after sending data to the nRF8001 for too long. It is pulled low by the lib from the time the data is send to the time the nRF8001 is ready to get the data. This is more then 1ms and way to long for a 1000Hz sampling from the sensor connected via SPI.

My quedtion is, is it possible to separate the REQN line from the chip select line? With a separation the SPI bus is blocked only when transmitting data via SPI.

In the lib a port named optional_chip_select is available but it seems like it is not used in the sdk.

[MBlau]

Thx for the answer!

I was playing around a litte bit with 3MHz SPI connection and got it sending some values in time. As the MCU needs about 600 - 680 micro seconds for calculations with the sensor values I had a few sample rate problems (but not much). It was working fine most of the time, but I was sending just one 2 Byte value instead of like 10 4 Byte values to the nRF8001.

I will go on trying, but I think I will give the nRF51822 a try to get no timing problems on the main CPU and let the nRF51822 do all the BLE work, just sending it the values over SPI from the MCU. This sound like being a more stable solution.

I'm sorry, but I have no SPI analyzer traces.

I have been testing again. When I send 20 Bytes (on one pipe) it takes too much time until the data is send, even with the nRF8001 SPI bus running at 3 MHz and the sensors SPI bus running at 20MHz. The pure SPI transfer would be fast enough, but the REQN line is pulled low for to long.

Maybe there is another solution cause I only send data via BLE every 10th cycle (100Hz). I could split up the data and send it between the next 9 cycles, but this just doesn't seam to be the right way to handle this. And send via one pipe the receiving device has to get the data back together...

[MBlau]

I need some tome to get into DMA. Never heard it before ;) But it sounds nice. I'm actually trying to get the nRF51822 running as SPI Slave with DMA too.