SPI end of TX

RE: SPI end of TX

hmolesworth — Thu, 18 Aug 2022 23:53:54 GMT

You're welcome but note you can do 3-wire SPI without a hardware hack or DCX which means you can use any of the 4 SPIM channels. I can post details if needed.

RE: SPI end of TX

Cecylia — Thu, 18 Aug 2022 23:13:43 GMT

That's a great idea! But, after discussing with the HW team, we ended up using 1 SPI and did some tricks to enable multiple slaves.

This DCX ended up getting used for our "hack" of a 3-wire SPI, btw. So when DCX is high, we send MOSI and when DCX is low, we get MISO 🙂.

We got it working now. Thanks again hmolesworth ! :D

RE: SPI end of TX

hmolesworth — Wed, 10 Aug 2022 21:25:48 GMT

You're very welcome. If you can spare another pin and don't require simultaneous SPI to both devices maybe use 2 x /CS, one for each device, and change the .cs pin before each transfer. The other signals can all be common between the devices.

RE: SPI end of TX

Cecylia — Wed, 10 Aug 2022 21:13:33 GMT

I ported the nrfx_spim driver from SDK 16's examples. I could successfully toggled the GPIO pin. Very nice!

I'm supposed to do this to 2 SPI, though. And, this extended feature only works for one SPI - SPIM3. I guess, I still need to figure out what to do with the other SPI.

This is very helpful, though. Thank you very much hmolesworth !

Edvin any other suggestions? At least for the other SPI?

Thanks,
Cecylia

RE: SPI end of TX

Cecylia — Wed, 10 Aug 2022 00:30:05 GMT

Cool! I saw nrfx_spim in the examples directory. So I'm going to try that first. Thanks so much hmolesworth !!

RE: SPI end of TX

hmolesworth — Tue, 09 Aug 2022 00:31:00 GMT

(NRFX_SPIM_EXTENDED_ENABLED needs to be set to enable the DCX stuff in nrfx_spim.h - DCX allows multiple lead bytes, probably what you are looking for. Common with some displays; may need later SDKs v17 on, not sure about SDK16 but you can copy the v17 stuff to v16, fairly straightforward.

RE: SPI end of TX

Cecylia — Mon, 08 Aug 2022 23:04:10 GMT

hmolesworth thanks! That sounds very much like what I'm looking for.

I'm going to find more examples on how to set the DCX pin. But, from quick browsing on the SDK, it looks like I will have to change the nrf_drv_spi_init() in the driver? Because during this SPI init, it will call SPIM init, but I don't see any code that sets 'dcx_pin'.

Did you have to change the driver, too?

ret_code_t nrf_drv_spi_init(nrf_drv_spi_t const * const p_instance,
                            nrf_drv_spi_config_t const * p_config,
                            nrf_drv_spi_evt_handler_t    handler,
                            void *                       p_context)
{
...

#ifdef SPIM_PRESENT
        nrfx_spim_config_t config_spim = NRFX_SPIM_DEFAULT_CONFIG;
        config_spim.sck_pin        = p_config->sck_pin;
        config_spim.mosi_pin       = p_config->mosi_pin;
        config_spim.miso_pin       = p_config->miso_pin;
        config_spim.ss_pin         = p_config->ss_pin;
        config_spim.irq_priority   = p_config->irq_priority;
        config_spim.orc            = p_config->orc;
        
// Where can we set the 'dcx_pin'??? Need to modify nrf_drv_spi_init??? 

        config_spim.frequency      = (nrf_spim_frequency_t)p_config->frequency;
        config_spim.mode           = (nrf_spim_mode_t)p_config->mode;
        config_spim.bit_order      = (nrf_spim_bit_order_t)p_config->bit_order;
        result = nrfx_spim_init(&p_instance->u.spim,
                                &config_spim,
                                handler ? spim_evt_handler : NULL,
                                (void *)inst_idx);
#endif

RE: SPI end of TX

hmolesworth — Fri, 05 Aug 2022 23:59:36 GMT

Maybe just use the DCX function available on SPIM3 to drive the pin

RE: SPI end of TX

Cecylia — Fri, 05 Aug 2022 23:25:56 GMT

Hi Edvin,

[quote userid="26071" url="~/f/nordic-q-a/90714/spi-end-of-tx/380409"]That depends on the application and the HW that you are connecting to. It depends on how many bytes that you expect to write, and how many bytes you expect to receive, if any. [/quote]

Suppose we're just sending one byte and expect to receive back one byte, how would you go about intercepting the code right before we receive back the MISO?

[quote userid="26071" url="~/f/nordic-q-a/90714/spi-end-of-tx/380409"]

This will give you a callback event spi_event_handler() in main.c when you receive data.

[/quote]

But I need to intercept before MISO comes in. The spi_event_handler() is typically called after the whole MOSI+MISO transaction is finished.

Thank you,
Cecylia

RE: SPI end of TX

Edvin — Fri, 05 Aug 2022 13:44:41 GMT

Hello Cecylia,

[quote user=""]

NRF_SPIM_EVENT_ENDTX

Is this the event where we just finished sending to MOSI and are about to receive from MISO?

[/quote]

That depends on the application and the HW that you are connecting to. It depends on how many bytes that you expect to write, and how many bytes you expect to receive, if any.

If you want to do some testing, you can test the example found in SDK\examples\peripheral\spi.

This will give you a callback event spi_event_handler() in main.c when you receive data.

Best regards,

Edvin