SPI Transaction manager - nCS (chip select behavior)

[eyalasko]

Hello, 

In my project (nRF52, SDK14.2) I have spi data flash connected to the MCU.

I'm trying to use SPI transaction manager library (nrf_spi_mngr) and face few questions:

1. Does .ss pin (in nrf_drv_spi_config_t) used in nrf_spi_mngr_init() serves as the chip select nCS?
2. If it does -
   1. How can I drive several spi components of the same spi port (each with a different nCS)?
   2. If I'm using nrf_spi_mngr_schedule() to schedule a transaction pointing to multiple transfers (nrf_spi_mngr_transaction_t.p_transfers), will nCS be deasserted-reasserted between consecutive transactions ?
      • If it does deassert-reassert between transfers, can it be overridden - i.e. sending multiple transfers WITHOUT deassert-reassert in between transfers (like address and then data etc)?
3. If it doesn't -
   1. How do I assert/deassert nCS before/after spi transfer. Do I use .begin_callback/end_callback of nrf_spi_mngr_transaction_t for that purpose?

Thanks.

[bjorn-spockeli]

Q1: Yes, the SS(Slave Select) is the same as CS(Chip Select).

Q2a: No, if you have multiple SPI Slaves, then you need to assert-deassert the SS lines yourself using the GPIO HAL. 

Q2b: See answer to Q2a.

Q3: Yes, using the begin_callback/end_callbacks to assert/deassert the SS line for a particular SPI slave is the way I would do it. 

Best regards

Bjørn