Add support for nRF52 Watchdog

[manchoz]

Description

Add the Watchdog driver implementation for the nRF52 targets using the nRF5 SDK WDT API.

To enable the Watchdog driver for the nRF2 targets, you need to activate it adding the macro NRFX_WDT_ENABLED=1 in the macro section of mbed_app.json configuration file and adding the "WATCHDOG" key to the list of the device's drivers. Example file:

{
    "macros": [
        "MBED_HEAP_STATS_ENABLED=1",
        "MBED_STACK_STATS_ENABLED=1",
        "MBED_MEM_TRACING_ENABLED=1",
        "NRFX_GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS=8",
        "NRFX_WDT_ENABLED=1"
    ],
    "target_overrides": {
        "*": {
        "platform.stdio-buffered-serial": true,
        "platform.stdio-baud-rate": 115200,
        "platform.default-serial-baud-rate": 115200
    },
    "ARDUINO_NANO33BLE": {
        "target.device_has_add": ["WATCHDOG"]
    }
}

Pull request type

[ ] Fix
[ ] Refactor
[X] Target update
[] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[ciarmcom]

@manchoz, thank you for your changes.
@ARMmbed/mbed-os-maintainers please review.

[0xc0170]

@manchoz Thanks for the contribution. I edited the comment above. There is no need for release notes (as this is just a target update). I'll review the code shortly

[0xc0170]

Questions:

• how was this tested
• why watchdog is not enabled for any current supported targets

[0xc0170]

SPDX identifiers please to new files

[manchoz]

Added SPDX for Apache-2.0.

[0xc0170]

Remaining questions:

• how was this tested
• why watchdog is not enabled for any current supported targets

[manchoz]

@0xc0170

Implementation has been tested on several Arduino Nano33Ble boards adapting the Watchdog example for the Arduino platform. The following sketch was used:

#include "mbed.h"
#include "drivers/Watchdog.h"

using namespace mbed;

REDIRECT_STDOUT_TO(Serial)

// Connect momentary button beetwen Pin 2 and GND
const byte interruptPin = 2;

// Maximum Watchdog timoute in seconds for nRF52840
// const int INIT_COUNTDOWN = 131071;

const int INIT_COUNTDOWN = 10;
int countdown = INIT_COUNTDOWN;

const uint32_t TIMEOUT_MS = countdown * 1000;

uint32_t now = millis();
const uint32_t interval = 1000;

uint32_t nowLed = millis();
uint32_t ledInterval = 1000;

void trigger()
{
    Watchdog::get_instance().kick();
    countdown = INIT_COUNTDOWN;
    ledInterval = 1000;
}

void setup()
{
    Serial.begin(115200);

    // Wait for connection on serial port
    while (!Serial)
        ;

    Serial.println();
    Serial.println("Target started ");
    Serial.println();

    pinMode(interruptPin, INPUT_PULLUP);
    attachInterrupt(digitalPinToInterrupt(interruptPin), trigger, FALLING);

    Watchdog &watchdog = Watchdog::get_instance();

    Serial.print("Enabling Watchdog. (");
    Serial.print((uint32_t)TIMEOUT_MS);
    Serial.println(" ms).");

    bool enabled = watchdog.start(TIMEOUT_MS);
    Serial.print("Status: ");
    Serial.println(enabled ? "Enabled": "Not Enabled");

    if (!enabled) {
        Serial.println("Timer not enabled. Invalid timeout parameter.");
        delay(2000);
        while (true);
    }

    uint32_t watchdog_timeout = watchdog.get_timeout();
    Serial.print("Watchdog initialized to ");
    Serial.print(watchdog_timeout);
    Serial.println(" ms.");

    Serial.print("Press BUTTON at least once every ");
    Serial.print(watchdog_timeout);
    Serial.println(" ms to kick the watchdog and prevent system reset");

    nowLed = millis();
    now = millis();
}

void loop()
{
    if (millis() - now > interval - (float)ledInterval / INIT_COUNTDOWN) {
        printf("\r%3i", countdown--);
        fflush(stdout);
        now = millis();
    }

    if (millis() - nowLed > ledInterval) {
        // Blink LED faster and faster as timout approaches
        digitalWrite(LED_BUILTIN, HIGH);
        delay(50);
        digitalWrite(LED_BUILTIN, LOW);
        ledInterval -= (float)ledInterval / INIT_COUNTDOWN;
        nowLed = millis();
    }
}

I really don't know why the watchdog for nRF52x have not been implemented yet on Mbed: it's implemented on almost any other RTOS.

[0xc0170]

I see, on Arduino Nano33Ble that does not support daplink (cant be tested with our infrastructure, correct?).

Looks fine to me and even better if we can enable this for a common nrf target that can be tested?

[manchoz]

@0xc0170

I have run a few tests with a Makerdiary nRF52850-MDK board (which supports DAPlink) in a standard Mbed OS scenario and everything seems ok.

Test code and instructions are at https://github.com/manchoz/mbed-os-example-watchdog-nrf52840.

(Please note that the repo contains also the support for the nRF52850-MDK board).

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts

[manchoz]

@0xc0170 @ARMmbed/mbed-os-maintainers Thank you so much!