SPI pin on nrf51 DK

[Yacire]

Hi All,

I have a question about the SPI pin number on nrf51 Dk.

I don't understand when i look into the pca10028.h file, i see this mapping:

#define SPIM0_SCK_PIN       4
#define SPIM0_MOSI_PIN      1
#define SPIM0_MISO_PIN      3
#define SPIM0_SS_PIN        2

But when i look into the nrf_drv_config.h file , i see this:

#if (SPI0_ENABLED == 1) #define SPI0_USE_EASY_DMA 0

#define SPI0_CONFIG_SCK_PIN 2 #define SPI0_CONFIG_MOSI_PIN 3 #define SPI0_CONFIG_MISO_PIN 4 #define SPI0_CONFIG_IRQ_PRIORITY APP_IRQ_PRIORITY_LOW

I don't understand what is SPI0_CONFIG_SCK_PIN, SPI0_CONFIG_MOSI_PIN and SPI0_CONFIG_MISO_PIN and why the pin mapping is not the same to pca10028.h ??

Thanks for your clarification.

[Jørgen Holmefjord]

Hi,

The pins on nRF51 (and nRF52) chips are reconfigurable via pin crossbar, meaning you can use any of the GPIO pins for any peripheral like SPI, UART, TWI, etc.

The defines in pca10028.h is just defines for default pinouts on the PCA10028 board, to easily be able to support for new boards in SDK. This is enabled by the Board Support Package.

The macros in nrf_drv_config.h is the actual configuration of the interface and its pins. If you change the pin numbers here, the new pins will be used for the SPI interface.

Best regards,

Jørgen

[Yacire]

Thanks for your answer Jorgen,

But i use bsp.h file, so my pin for the SPI interface are those defined in the pca10028.h right ? The pin defined in the nrf_drv_config.h are used if i don't use the bsp.h file ?

[Jørgen Holmefjord]

No, the defines in nrf_drv_config.h is used to setup the SPI interface (given that you are using the SPI master driver). If you want to use the pins defined in BSP, you need to change the defines in nrf_drv_config.h to:

#define SPI0_CONFIG_SCK_PIN SPIM0_SCK_PIN

#define SPI0_CONFIG_MOSI_PIN SPIM0_MOSI_PIN

#define SPI0_CONFIG_MISO_PIN SPIM0_MISO_PIN

[Yacire]

Are you sure ?

I tested the SPI Master LoopBack example and it is the pins defined in the bsp.h file who are used for SPI... Not those in the nrf_drv_config.h

Can you test the example in the SDK 10 ? connect pin 1 and 3 for SPI0, and 12 and 14 for SPI1 and it works.

But if you look in the nrf_drv_config, you can see the SPI0 and SPI1 are enabled and the pin mapping is the same: pin 2 3 and 4.

I don't understand. Thanks.

[Jørgen Holmefjord]

Yes, in the SPI Loopback example in SDK10 it is correct that the pins from BSP is used. If you look at the function spi_master_init(..) in main.c, you can see that the nrf_drv_spi_config_t is set to use the pin numbers defined in pca10028.h. If you change the example to use the default config using nrf_drv_spi_config_t config = NRF_DRV_SPI_DEFAULT_CONFIG(0);, as described in the spi master driver documentation, the pins from the defined in nrf_drv_config.h would have been used. It all depends on how the SPI interface is configured.