I2C Crashes Kernel on Raspberry Pi Pico

[tanneberger]

Description

I want to use the veml7700 brightness sensor in combination with the Raspberry Pi PICO. Sadly, RIOT crashes after calling i2c_init (see the code below).

I tested the same code on the feather-nrf52840-sense there it works flawlessly.

int main(void) {
    i2c_t dev = I2C_DEV(0);
    i2c_init(dev); // crashes here

    uint16_t reg_value = 0;
    uint16_t device_addr = 0x10;

    i2c_acquire(dev);

    uint16_t conf_val1 = 6144;
    printf("writing value: %i", conf_val1);

    i2c_write_byte(dev, device_addr, 0, I2C_NOSTOP);
    i2c_write_bytes(dev, device_addr, &conf_val1, 2, 0);


    while (true) {
        i2c_read_regs(dev, device_addr, 0x04, &reg_value, 2, 0);
        printf("%i\n", reg_value);
    }

    i2c_release(dev);
    return 0;
}

Output I get by connecting a logic analyzer:

Steps to reproduce the issue

In the Makefile, I add the line USEMODULE += periph_i2c in order to use i2c. Just compile this program for the BOARD=rpi-pico

Expected results

Don't crash.

Versions

I run this on RIOT version 2024.10 (b51f093a395bdd575cff94b7d26be415fa46771d)

[maribu]

Thx for the report. Could you try again without i2c_init()?

(Alternatively you could disable the auto initialisation of the I2C buses and then do by hand. I'm afk, but I think the module is named periph_init_i2c that does the auto initialisation. You can add DISABLE_MODULE += periph_init_i2c to the apps Makefile for that; assuming that I correctly nemorized the module name.)

[dylad]

Hi @tanneberger
As @maribu suggested, you can try without i2c_init() as this part is in general done automatically for you by RIOT.
Except if you use DISABLE_MODULE += periph_init_i2c
You can check this with make -C path/to/your/app info-build if you are uncertain. (Look at the USEMODULE / DISABLE_MODULES).

However, a second call to i2c_init() should not hurt that much so there is definitely something wrong underneath.

[maribu]

However, a second call to i2c_init() should not hurt that much so there is definitely something wrong underneath.

That is not generally true. Most MCU peripherals are initialized in a way that the code is naturally idempotent. But some periph drivers rely on being called exactly once.

Our documentation in again substandard here, but in https://doc.riot-os.org/group__drivers__periph.html#autotoc_md1719 it is hinted.

[dylad]

Perhaps we could keep track of the state of the peripheral and early return if the initialization was already done or trigger an assert.
A Kernel panic is a high price to pay for a periph reinit.

[maribu]

@tanneberger: This issue to be auto-closed upon merge, rather than by intent, because I wrote maybe fixes #21187 in PR #21188.

Could you you report back if the issue was indeed the second call to i2c_init()?

And sorry for the doc being wrong here :/

[miri64]

Could you you report back if the issue was indeed the second call to i2c_init()?

Let's re-open the issue until then.