nRF52840 SPI question

[Pranav Sanghadia]

Hi,

Can someone help me with question on SPI?

What is the difference between SPIM and SPI? They seem to have different clocks Also in the SPIM section, the frequency is said to be 32MHz in a number of places but then in one table again it is listed as 8Mbps. (which might be a typo) what do you make of this?

[Roger Clark]

SPIM is where the MCU is the SPI Master (this is what you'd use to connect to a SPI peripheral e.g. a sensor.

Re: SPI Frequency

Normally you configure the frequency as part of the SPI driver initialisation

e.g.

	uint8_t error;

	nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;	


	spi_config.frequency    = NRF_DRV_SPI_FREQ_8M;   
	spi_config.ss_pin   = 4;
	spi_config.sck_pin  = 5;
	spi_config.miso_pin = 6;
	spi_config.mosi_pin = 7;


	error = nrf_drv_spi_init(&spiBMP280, &spi_config, NULL);

[SRA]

Exactly. SPIM is just SPI Master.

[ovrebekk]

Hi Pranav

The SPI interface is the old legacy SPI master carried over from the nRF51 series. The SPIM is the new SPI master that uses DMA, originally introduced in the nRF52832.

So far we have kept the SPI interface for backwards compatibility (so you can easily port code from the nRF51/nRF52832 that uses it), but it might be removed in future products, so I would recommend using the SPIM instead. The SPIM interface is also more efficient since all the data transfer is handled by the DMA controller.

The 32MHz mode refers to the new high speed SPIM interface in the nRF52840. Unfortunately this interface is unavailable in the preview part you have today, but it will be added to the production part released towards the end of the year. This will be the NRF_SPIM3 interface, which means you still have all the old SPI and SPIM interfaces available (limited to 8MHz).

Best regards
Torbjørn

[sean]

can I use spi 32bps on nrf52832? 32bps only on nrf52840?

[sean]

The spi clock of nrf52832 toooo low, anyone know howto set spi clock to 16M