Configuring MISO pin for SPIM nrf52

[troglobyte]

Greetings I am working on an application that logs data to SPI flash device. I am having an issue where it appears that the pin configured as a MISO for SPIM is garbling up the flash device's responses. I have verified with a logic analyzer that the device response is correct when unloaded and gets corrupted when terminated into the Nordic development board (pca10040). I have noted the same behavior for all pins on the nrf52. I have also used a number of different flash devices (Adesto AT25XE021A type devices) all with the same result. After the spi peripheral is initialized, the application attempts to read the device ID from the flash module. The correct response should be 0x1F, 0x43, 0x01, 0x00 but instead I read 0x1E, 0x08, 0x00, 0x00...

I have included my init code for inspection and have also noted that there is an errata where the Pin CNF gets reset whenever the device goes to sleep when in debug interface mode.

Here is how my pins are defined in nrf_drv_config.h...

#define SPI1_ENABLED 1

#if (SPI1_ENABLED == 1)
#define SPI1_USE_EASY_DMA 1

#define SPI1_CONFIG_SCK_PIN         25
#define SPI1_CONFIG_MOSI_PIN        23
#define SPI1_CONFIG_MISO_PIN        24
#define SPI1_CONFIG_IRQ_PRIORITY    APP_IRQ_PRIORITY_LOW

#define SPI1_INSTANCE_INDEX (SPI0_ENABLED)
#endif

This is the inline function called to configure the GPIO for the MISO input...

__STATIC_INLINE void nrf_gpio_cfg_input(uint32_t pin_number, nrf_gpio_pin_pull_t pull_config) {
    nrf_gpio_cfg(
            pin_number,
            NRF_GPIO_PIN_DIR_INPUT,
            NRF_GPIO_PIN_INPUT_CONNECT,
            pull_config,
            NRF_GPIO_PIN_S0S1,
            NRF_GPIO_PIN_NOSENSE); }

I have verified that the correct code is being called during initialization (SPI Master mode code) and am using the latest SDK code implementing the spi driver.

Other than the above mentioned errata, what could be causing the MISO signal to act as though it is being driven by the nrf52 even though it is configured as an input?

Any info would be appreciated!

Trog

[Ole Bauck]

How do you know that the nRF52 is driving the line other than that what you read is incorrect?

[troglobyte]

The signal connects only to the nrf52 on this development board. There are no other drivers (or receivers for that matter). I have ohmed the signal to ground and is high impedance. Also note that this happens with every pin that I try on the nrf52 dev board.

[troglobyte]

I will also add that the version of the dev board is PCA10040 V 0.9.0 2015.49

[Sir Oslay]

I'm having the same issue with an Adesto AT45DB041E flash chip on the PC10040 board. The program reads complete garbage when MISO is connected to the board. When I disconnect MISO I can see on my scope that the correct info is being sent. Something is interfering with whatever pin is configured as the MISO input.

[Sir Oslay]

I was having the same issue with an Adesto AT45DB041E flash chip on the PC10040 board. I ended up getting it to work by putting a current limiting resistor in series with the MISO line. I used a 39 ohm resistor because it happened to be the only resistor I had on hand at the time. If there's a more suitable value, please let me know!