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.

[David Edwin]

Let me try to understand your question by re-phrasing it. You are sharing the SPI with the nRF8001 and a sensor and the sensor needs to be sampled once every 1000 times a second i,e, once every millisecond. I will assume that the sensor SPI takes about 100 micro seconds.

This means that the nRF8001 transaction must finish within 900 micro seconds, you need to run the SPI at its fastest i.e. 3MHz and also reduce the interbyte distance on the SPI.

It is also possible to bit bang an SPI on separate lines as the option of last resort so that the sensor is not disturbed and the nRF8001 can also operate.

Is my understanding correct ?

Do you think you can share some SPI analyzer traces, with REQN, RDYN and the SPI lines.