How to Use SPI Interface in a Zephyr sample example?

RE: How to Use SPI Interface in a Zephyr sample example?

Håkon Alseth — Tue, 12 Jan 2021 10:05:33 GMT

Hi Ram,

I slightly modified the samples, so that it sets up RX and TX transaction on the master side, and increments the first byte in the payload (cycles through ascii '0' to '9').

I do not have two nrf52840dk's at my end at this point, so I'm using a nRF9160-DK as the master, but it should be possible to use nRF52/nRF53/nRF91 with no or little modifications. I tested both examples on a nRF52840 (ie: reversed the SPI roles)

nRF52840 is the SPIS in my end with the below prints.

Master should print like this when properly connected to the slave, and sends once per second (note: it prints in hex)

*** Booting Zephyr OS build v2.4.0-ncs2 ***
SPIM example
IRQ: 0
Transfer completed
Received: 35 36 37 38 39 30 31 32 33 34 0 0
IRQ: 0
Transfer completed
Received: 35 36 37 38 39 30 31 32 33 34 0 0

Slave should print this:

*** Booting Zephyr OS build v2.4.0-ncs2 ***
SPIS example
ISR 0
ISR 1
bytes rx: 11
7234567890ISR 0
ISR 1
bytes rx: 11
8234567890ISR 0
ISR 1
bytes rx: 11
9234567890ISR 0

Here you should see that the first byte increments.

The actual bus communication should look like this (here sampled with a logic analyzer from Saleae):

Here are my projects:

devzone.nordicsemi.com/.../nrfx_5F00_spi_5F00_master.zip

devzone.nordicsemi.com/.../nrfx_5F00_spi_5F00_slave.zip

If you, after flashing and connecting SPIS -> SPIM, still do not receive or send data as expected, could you please use a logic analyzer to see if there's anything happening on the SPI pins?

Kind regards,

Håkon

RE: How to Use SPI Interface in a Zephyr sample example?

RAS_ID — Mon, 11 Jan 2021 15:58:58 GMT

Hi Hakon,

Thanks for your prompt reply!

I have updated the pin ordering in the configuration on both sides. I have also changed the number of bytes to send.

Is the setup for the event handler correct? I am ready to share my screen with you if you have a few minutes?

Let me know.

Thanks

Ram

RE: How to Use SPI Interface in a Zephyr sample example?

Håkon Alseth — Mon, 11 Jan 2021 10:38:04 GMT

Hi Ram,

1Ordering of your pins are incorrect when you're configuring:

static nrfx_spis_config_t spis_config = NRFX_SPIS_DEFAULT_CONFIG(APP_SPIS_CS_PIN,
APP_SPIS_MISO_PIN,APP_SPIS_MOSI_PIN,APP_SPIS_SCK_PIN);

static nrfx_spim_config_t spim_config = NRFX_SPIM_DEFAULT_CONFIG(APP_SPIM_CS_PIN,
APP_SPIM_MISO_PIN,APP_SPIM_MOSI_PIN,APP_SPIM_SCK_PIN);

Given that its equal on both sides, it should work, but be aware that the correct ordering according to the helper-macro should be:

NRFX_SPIS_DEFAULT_CONFIG(APP_SPIS_SCK_PIN, APP_SPIS_MOSI_PIN, APP_SPIS_MISO_PIN, APP_SPIS_CS_PIN);

NRFX_SPIM_DEFAULT_CONFIG(APP_SPIM_SCK_PIN, APP_SPIM_MOSI_PIN, APP_SPIM_MISO_PIN, APP_SPIM_CS_PIN);

The SPIM implementation seems to send 254 bytes, you should restrict this to the max. size of the m_tx_buf.

Have you scoped the pins using a logic analyzer to see if everything is setup correctly on a hardware level?

Kind regards,

håkon

RE: How to Use SPI Interface in a Zephyr sample example?

RAS_ID — Mon, 11 Jan 2021 06:58:45 GMT

Hi Hakon,

Thanks for your reply!

I have decided to use nrfx SPI driver at this time instead of Zephyr SPI port, and I have created two simple projects (using minimal) to run on two separate nRF52840dk: one for the master and the other for the slave. I start the slave and then start the master. The interrupt handler is called on the slave but the rx_amount is showing 0. I also noticed that interrupt handler on master is called but nrfx_spim_xfer() returns an error code. The prj.conf files for the two projects and the main.c are attached here.

Slave:

CONFIG_SPI=n
CONFIG_NRFX_SPIS=y
CONFIG_NRFX_SPIS1=y

CONFIG_MAIN_STACK_SIZE=4096

---------------------------------------------------

Master:

CONFIG_SPI=n
CONFIG_NRFX_SPIM=y
CONFIG_NRFX_SPIM1=y
CONFIG_MAIN_STACK_SIZE=4096

//main on SPI master
#include "nrfx_spim.h"
#include "nrfx_gpiote.h"
#include "drivers/nrfx_errors.h"
#include <sys/printk.h>
#include <string.h>

#define SPI_INSTANCE  1
static const nrfx_spim_t spim = NRFX_SPIM_INSTANCE(SPI_INSTANCE);

#define APP_SPIM_CS_PIN     0x10

#define APP_SPIM_SCK_PIN    0x1F
#define APP_SPIM_MISO_PIN   0x28
#define APP_SPIM_MOSI_PIN   0x1E

#define NRFX_CUSTOM_ERROR_CODES 0 //used in nrfx_errors.h

static nrfx_spim_config_t spim_config = NRFX_SPIM_DEFAULT_CONFIG(APP_SPIM_CS_PIN,   
                                     APP_SPIM_MISO_PIN,APP_SPIM_MOSI_PIN,APP_SPIM_SCK_PIN);
 
#define TEST_STRING "1234567890"
static uint8_t       m_tx_buf[] = TEST_STRING;
static uint8_t       m_rx_buf[sizeof(TEST_STRING) + 1];
static const uint8_t m_length = sizeof(m_tx_buf);

static volatile bool spim_xfer_done; /**< Flag used to indicate that SPIM instance completed the transfer. */

static void manual_isr_setup()
{
    IRQ_DIRECT_CONNECT(SPIM1_SPIS1_TWIM1_TWIS1_SPI1_TWI1_IRQn, 0, nrfx_spim_1_irq_handler, 0);
    irq_enable(SPIM1_SPIS1_TWIM1_TWIS1_SPI1_TWI1_IRQn);
}
 
void spim_event_handler(nrfx_spim_evt_t const * p_event,
                       void * p_context)
{
    if(p_event->type == NRFX_SPIM_EVENT_DONE)
    {
        spim_xfer_done = true;
        printk("Transfer completed.");
    }
}
 
void main(void)
{
    printk("SPIM example");
    nrfx_spim_xfer_desc_t xfer_desc = NRFX_SPIM_XFER_TX(m_tx_buf, 254);
 
    if (NRFX_SUCCESS != nrfx_spim_init(&spim, &spim_config, spim_event_handler, NULL))
    {
      printk("Init Failed");
      return;
    }

    manual_isr_setup();
 
//   while (1)
//    {
        // Reset rx buffer and transfer done flag
        memset(m_rx_buf, 0, m_length);
        spim_xfer_done = false;
 
        nrfx_err_t err_code = nrfx_spim_xfer(&spim, &xfer_desc, 0);
 
	if (err_code == NRFX_ERROR_BUSY)
	{
		printk("SPI busy");
	}
        
	else
	{
		printk("Error code = %d",err_code);
	}
        
 
        while (!spim_xfer_done)
        {
            __WFE();
        }
 
//        nrfx_delay_ms(1000);
//    }
}

//main on SPI slave
#include "nrfx_spis.h"
#include "nrfx_gpiote.h"
#include <sys/printk.h>

#include <string.h>
#include <irq.h>

#define SPIS_INSTANCE 1 /**< SPIS instance index. */
static const nrfx_spis_t spis = NRFX_SPIS_INSTANCE(SPIS_INSTANCE);/**< SPIS instance. */

#define APP_SPIS_CS_PIN     0x10

#define APP_SPIS_SCK_PIN    0x1F
#define APP_SPIS_MISO_PIN   0x28
#define APP_SPIS_MOSI_PIN   0x1E

static nrfx_spis_config_t spis_config = NRFX_SPIS_DEFAULT_CONFIG(APP_SPIS_CS_PIN,   
                                     APP_SPIS_MISO_PIN,APP_SPIS_MOSI_PIN,APP_SPIS_SCK_PIN);
#define TEST_STRING "5678901234"
static uint8_t       m_tx_buf[] = TEST_STRING;           /**< TX buffer. */
static uint8_t       m_rx_buf[sizeof(TEST_STRING) + 1];    /**< RX buffer. */

static const uint8_t m_length = sizeof(m_tx_buf);        /**< Transfer length. */


static volatile bool spis_xfer_done; /**< Flag used to indicate that SPIS instance completed the transfer. */

static void manual_isr_setup()
{
    IRQ_DIRECT_CONNECT(SPIM1_SPIS1_TWIM1_TWIS1_SPI1_TWI1_IRQn, 0, nrfx_spis_1_irq_handler, 0);
    irq_enable(SPIM1_SPIS1_TWIM1_TWIS1_SPI1_TWI1_IRQn);
}

/**
 * @brief SPIS user event handler.
 *
 * @param event
 */
void spis_event_handler(nrfx_spis_evt_t * event, 
                        void * p_context)
{
    if (event->evt_type == NRFX_SPIS_XFER_DONE)
    {
      spis_xfer_done = true;
      printk("Transfer completed. Received: %d",event->rx_amount);
    }
}

int main(void)
{
    // Enable the constant latency sub power mode to minimize the time it takes
    // for the SPIS peripheral to become active after the CSN line is asserted
    // (when the CPU is in sleep mode).
    NRF_POWER->TASKS_CONSTLAT = 1;

    printk("SPIS example");

    
    if (NRFX_SUCCESS != nrfx_spis_init(&spis, &spis_config, spis_event_handler, NULL))
    {
      printk("Init Failed");
      return 0;
    }

    manual_isr_setup();

    while (1)
    {
        memset(m_rx_buf, 0, m_length);
        spis_xfer_done = false;

        if (NRFX_SUCCESS != nrfx_spis_buffers_set(&spis, m_tx_buf, m_length, m_rx_buf, m_length))
        {
          printk("Receive Failed");
          return 0;
        }

        while (!spis_xfer_done)
        {
            __WFE();
        }
    }
}

*** Booting Zephyr OS build v2.4.0-ncs1-3-gfe00929d308d ***
SPIM example Error ransfer completed.code = 195887104 (this is due to coding issue but this is NRFX_SUCCESS)

*** Booting Zephyr OS build v2.4.0-ncs1-3-gfe00929d308d ***
SPIS example Transfer completed. Received: 0 It means slave is seeing the interrupt without any data.

Could you please see the .config and main files and guide me what is missing for slave not reading the data?

Thanks,

Ram

RE: How to Use SPI Interface in a Zephyr sample example?

Håkon Alseth — Wed, 06 Jan 2021 16:43:46 GMT

Hi Ram,

[quote user="RAS_ID"]

Thanks for your detailed reply! I really appreciate it! I have the following details from other Nordic posts.

1. In https://devzone.nordicsemi.com/f/nordic-q-a/69269/issues-with-implementing-spi-slave-on-nrf9160dk/285345#285345

you have replied that "The problem is that the nrfx_spis and zephyr's spi slave do not play well together, so you have to only have one of these enabled to be able to use the SPIS properly.

As your project is setup now, the zephyr spi driver will be initialized "post kernel" (see here: https://github.com/nrfconnect/sdk-zephyr/blob/master/drivers/spi/spi_nrfx_spis.c#L290-L297), and before main() is called.

This means that the spis_nrfx_spis.c implementation will then claim the SPIS3 peripheral before you can via the nrfx_spis API in main."

2. Also, you have written in https://devzone.nordicsemi.com/f/nordic-q-a/69034/nrf52840-spi-slave-configuration-event_handler

"The zephyr spis driver assumes that you use a dedicated thread, and use the k_poll functionality (signalled from the evt handler)", and

"If you use nrfx_spis (CONFIG_NRFX_SPIS=y) directly; you can do this using the approach with a event_handler."

3. And, Torbjorn has written in https://devzone.nordicsemi.com/f/nordic-q-a/56857/understanding-spi-with-easy-dma

There is no need to enable NRFX_SPIM_ENABLED or NRFX_SPI_ENABLED. As long as you enable SPI_ENABLED, and enable SPIx_USE_EASY_DMA for any instance that you use, the nrfx_spim driver will be enabled automatically, and DMA will be used.

If you want SPI slave you should enable SPIS_ENABLED

Please note that there is no choice of DMA or not when using SPI slave, as the SPI slave peripheral had DMA from the start.

Note: I am not sure if this is applicable to SPI in nRF Connect or not.

[/quote]

Torbjørn is talking about the nrfx integration in the nRF5 SDK, by configuring the SPI/SPIM module using the sdk_config.h.

On the nRF52-series devices, in addition to the NRF_SPIM (DMA capable) module, there's a legacy NRF_SPI module, which is not DMA capable. The DMA mentions here are towards backwards compatibility.

nRF9160 does not have the legacy NRF_SPI module, so you'll have to use a DMA capable one here.

[quote user="RAS_ID"]

So, if I want to use easyDMA without a dedicated thread, I should set

CONFIG_NRFX_SPIS=y

CONFIG_NRFX_SPIS3=y

Form the documentation, CONFIG_SPI_0_NRF_SPIS enables nRF SPI slave with EasyDMA on port-0. It is indirectly enabled with SPI_SLAVE && SPI_NRFX && SPI. It means that all the 3 shall be set to y in my configuration.

[/quote]

The CONFIG_NRFX_* configs allow you to directly access the nrfx driver. This then omits DTS and other configs towards the zephyr SPI component. You should then set CONFIG_SPI=n to avoid zephyr potentially "grabbing" your NRF_SPIx interrupt vector, which it will do if you enable the same instance as you try to use with nrfx_spi*.

If you do not plant to use any of the sensor drivers or other functions related to zephyrs driver, you can set CONFIG_NRFX_SPIS=y and include nrfx_spis.h in your application, and setup the driver directly, similar to how its done in the nRF5 SDK example examples/peripheral/spis.

Note: when using NRFX drivers, you have to manually link the interrupt vector, similar to this:

https://github.com/Rallare/fw-nrfconnect-nrf/blob/nrf9160_samples/samples/nrf9160/nrfx_timed_signal/src/main.c#L128-L132

Kind regards,

Håkon

[quote user="RAS_ID"]Could you please throw some light on the configuration for the SPI master and SPI slave with DMA and without DMA without a dedicated thread?[/quote]

You have to use DMA on a hardware level.

If you want to use the SPI modules with any of the drivers/sensors in the zephyr tree, you should look at using the zephyr spi driver. However, if not, you can choose freely between the zephyr SPI or use nrfx directly.

RE: How to Use SPI Interface in a Zephyr sample example?

Håkon Alseth — Wed, 06 Jan 2021 08:09:34 GMT

Hi Ram,

[quote user="RAS_ID"]

One more question. What are these 3 configurations?

CONFIG_NRFX_SPI

CONFIG_NRFX_SPIM

CONFIG_NRFX_SPIS

[/quote]

This brings in the nrfx driver, which the zephyr spi port driver uses:

https://github.com/nrfconnect/sdk-hal_nordic/blob/master/CMakeLists.txt#L66

Kind regards,

Håkon

RE: How to Use SPI Interface in a Zephyr sample example?

RAS_ID — Wed, 06 Jan 2021 07:08:10 GMT

Hi Hakon,

One more question. What are these 3 configurations?

CONFIG_NRFX_SPI

CONFIG_NRFX_SPIM

CONFIG_NRFX_SPIS

Thanks,

Ram

RE: How to Use SPI Interface in a Zephyr sample example?

RAS_ID — Tue, 05 Jan 2021 21:29:39 GMT

Hi Hakon,

Thanks for your detailed reply! I really appreciate it! I have the following details from other Nordic posts.

1. In https://devzone.nordicsemi.com/f/nordic-q-a/69269/issues-with-implementing-spi-slave-on-nrf9160dk/285345#285345

you have replied that "The problem is that the nrfx_spis and zephyr's spi slave do not play well together, so you have to only have one of these enabled to be able to use the SPIS properly.

This means that the spis_nrfx_spis.c implementation will then claim the SPIS3 peripheral before you can via the nrfx_spis API in main."

2. Also, you have written in https://devzone.nordicsemi.com/f/nordic-q-a/69034/nrf52840-spi-slave-configuration-event_handler

"The zephyr spis driver assumes that you use a dedicated thread, and use the k_poll functionality (signalled from the evt handler)", and

"If you use nrfx_spis (CONFIG_NRFX_SPIS=y) directly; you can do this using the approach with a event_handler."

3. And, Torbjorn has written in https://devzone.nordicsemi.com/f/nordic-q-a/56857/understanding-spi-with-easy-dma

If you want SPI slave you should enable SPIS_ENABLED

Please note that there is no choice of DMA or not when using SPI slave, as the SPI slave peripheral had DMA from the start.

Note: I am not sure if this is applicable to SPI in nRF Connect or not.

My questions:

So, if I want to use easyDMA without a dedicated thread, I should set

CONFIG_NRFX_SPIS=y

CONFIG_NRFX_SPIS3=y

Do I need to set CONFIG_SPI_0_NRF_SPIS=y?

There are so many configuration available to use SPI.

Could you please throw some light on the configuration for the SPI master and SPI slave with DMA and without DMA without a dedicated thread?

Thanks,

Ram

RE: How to Use SPI Interface in a Zephyr sample example?

Håkon Alseth — Tue, 05 Jan 2021 13:18:00 GMT

Hi,

[quote user=""]

I see that DEVICE_INIT() in main.c and DEVICE_AND_API_INIT(1) in spi_nrfx_spi.c do all the initialization based on the board dts file. And, I could use spi_read(), spi_write(), spi_transceive() as appropriate to send/receive data thru SPI interface.

Is my understanding correct?

[/quote]

Yes, this correct when looking at the driver model in zephyr. Its ofcourse a bit more complex than this (see here: https://docs.zephyrproject.org/latest/reference/drivers/index.html), but this is a good overview.

Related to SPIM vs SPIS, there's some information here that might be of interest (DTS property naming can be confusing on SPIM/SPIS):

https://devzone.nordicsemi.com/f/nordic-q-a/69269/issues-with-implementing-spi-slave-on-nrf9160dk/285345#285345

There's an example specific to nrf5340 here:

https://devzone.nordicsemi.com/f/nordic-q-a/67065/how-to-configure-and-setup-an-spi-device-to-nrf5340

But, you can remove this line in CMakeLists.txt to allow configuring for other boards:

# remove these lines from CMakeLists.txt to build for other boards
set(NRF_SUPPORTED_BOARDS
  nrf5340pdk_nrf5340_cpuapp
  )

Then create your own $(BOARD).overlay file with your wanted configuration.

Note that the sample lacks CSN pin handling.

Kind regards,

Håkon