MCP2518 SPI-CAN integration with nrf52840

[Midhunjac]

Hi,

I am using nrf52840 on a custom board. I have a MCP2518 to which I wish to communicate through the SPI interface. I changed the dts file accordingly and added the bindings and finally got it to build. The problem is I cannot access the SPI bus. My custom driver is based on the mc2518 driver that is part of NRF Connectv2.2.0 . I have modified it and removed everything except the initialization part where it checks if the devices and bus is ready. I have not started using that however. I cannot get an instance of the MCP2518 because the initialization fails. The failure point is where it checks whether the SPI bus is ready. Exactly this same position as described in this post. It seems like that question is inactive now. So I though I would raise this question here. I hope it is alright.

There are a few additional observations too. If i do device_is_ready() on the SPI bus instance from main() of my application, it returns success. However, if I do the same check in my custom driver module, right before the above failure point, I get failure. I dont know if this bit of info helps and I dont know why it behaves differently.

I would very much appreciate it if anyone could help.

device ; nrf52840

NCS v2.2.0

trying to interface mcp2518fd

[Håkon Alseth]

Hi,

 

How is your overlay for the chosen "zephyr,canbus" and the spi-overlay for the mcp-IC?

Are you able to post any logs? You can for instance use SeggerRTT for logging if you do not have uart output.

I would strongly recommend that you connect a logic analyzer to the SPI pins to your mcp-IC, to see how the communication looks.

 

Kind regards,

Håkon

[Midhunjac]

Hi,

This is the relevant part of my overlay file.

spi_can:&spi0 {

    compatible = "nordic,nrf-spi";

    status = "okay";

    cs-gpios = <&gpio0 18 GPIO_ACTIVE_LOW>; /* D10 */

    pinctrl-0 = <&spi0_default>;

    pinctrl-1 = <&spi0_sleep>;

    pinctrl-names = "default", "sleep";

};

&spi_can {

    status = "okay";

    cs-gpios = < &gpio0 18 GPIO_ACTIVE_LOW >;

    mcp2518: can@0 {

        compatible = "microchip,mcp2518";

        spi-max-frequency = <1000000>;

        status = "okay";

        reg = <0x0>;

        int-gpios = <&gpio0 15 GPIO_ACTIVE_LOW>;

        osc-freq = <20000000>;

        bus-speed = <125000>;

        sjw = <1>;

        sample-point = <875>;

        can-transceiver {

            max-bitrate = <8000000>;

        };

    };

};

&pinctrl {

    status = "okay";

    uart0_default: uart0_default {

        group1 {

            psels = <NRF_PSEL(UART_TX, 0, 6)>,

                <NRF_PSEL(UART_RX, 0, 8)>;

        };

    };

    uart0_sleep: uart0_sleep {

        group1 {

            psels = <NRF_PSEL(UART_TX, 0, 6)>,

                <NRF_PSEL(UART_RX, 0, 8)>;

            low-power-enable;

        };

    };

    spi0_default: spi0-default {

        group1 {

            psels = <NRF_PSEL(SPIM_SCK, 0, 19)>,

                <NRF_PSEL(SPIM_MISO, 0, 21)>,

                <NRF_PSEL(SPIM_MOSI, 0, 23)>;

        };

    };

    spi0_sleep: spi0-sleep {

        group1 {

            psels = <NRF_PSEL(SPIM_SCK, 0, 19)>,

                <NRF_PSEL(SPIM_MISO, 0, 21)>,

                <NRF_PSEL(SPIM_MOSI, 0, 23)>;

        };

    };

};

I do not have any logs to post. There is nothing worth while from the UART console. I will have a look with the analyzer and try to find if there is something going on.

[Håkon Alseth]

This line:

compatible = "nordic,nrf-spi";

 

Should be:

compatible = "nordic,nrf-spim";

The only scenario where you want to use "nordic,nrf-spi" is for nRF52832, to avoid errata 58:

https://infocenter.nordicsemi.com/topic/errata_nRF52832_Rev3/ERR/nRF52832/Rev3/latest/anomaly_832_58.html#anomaly_832_58

 

The CAN sample is looking for a device compatibility for "zephyr,canbus". This seems to be missing on your end.

You should add a root for the chosen canbus device in your .overlay:

/ {
    chosen {
        zephyr,canbus = &mcp2518;
    };
};

 

Kind regards,

Håkon

[Midhunjac]

Hi,

Sorry for the misdirecting you with the chosen {} part. I have defined all this in my dts for the custom board and i have the 'chosen' node there.

chosen {

        zephyr,sram = &sram0;

        zephyr,flash = &flash0;

        zephyr,code-partition = &slot0_partition;

        zephyr,shell-uart = &uart0;

        zephyr,console = &uart0;

        zephyr,spi = &mcp2518;  

        zephyr,spi0 = &spi0;    

    };

I guess that is all good there then. right ?

I changed the line to compatible = "nordic,nrf-spim"; as you suggested. But it did not solve my problem. Is there some option I need to set ?

Currently I have CONFIG_CAN and CONFIG_SPI enabled in prj.conf. if I disable either of them, I get error while compiling.

So i guess I need them. Anything else you think I am missing here ?

[Håkon Alseth]

Hi,

 

The zephyr,canbus device is not chosen. Could you try adding this to your "chosen" list?

zephyr,canbus = &mcp2518;

 

Kind regards,

Håkon