MCU hang after toggling "strobe"

[MaxVandenbussche]

Hello.

I want to use the i2c keypad plugin. But everytime the strobe-pin is pulled low, the MCU hangs and needs to be reset. There is also no toggling on the i2c SDA and SCL lines. Any ideas?

Br, Max

[terjeio]

Which driver?

[MaxVandenbussche]

IMXRT1062 running on a Teensy 4.1 mounted on a grblHAL Breakout Board Unkit for Teensy 4.1.

[phil-barrett]

Are you using pre-built binaries?

[terjeio]

My test keypad (modified for pulling the strobe pin low) works with this setup. I'll have to revisit the iMXRT1020 I2C code, it is possible it should be "hardened" by adding a timeout if the keypad does not respond in time?

Have you made and written code for the keypad yourself?

[MaxVandenbussche]

I am building my own keypad and writing my own code for a different MCU. Indeed, I used the code for the MSP430 as a reference.

In any case it would be a good idea to have a timeout if the keypad does not respond in time to not have the whole system hang. This was my first thought. But after I pull the strobe low I never even get a falling edge on the SCL line. I assume the master should at least address the slave once. So I think this is not a timeout problem.

[terjeio]

The I2C code is interrupt driven with callback and will hang on the second attempt to address the keypad if the first one never completes. So a plain timeout will not work. I'll have to see how I can work around that.

Since my keypad work something must be amiss with your setup, even a broken MCU?

Is the keypad module reported in the $I report? The correct board is selected? Is SCL, SDA and strobe pins at 3.3V after bootup? What are they after the first strobe?

You may replace while(i2cIsBusy); in the code below with if(i2cIsBusy) return; as a temporary workaround for the hang.

https://github.com/terjeio/grblHAL/blob/f85da79de95db12eff347f146f862bdfbb4f683d/drivers/IMXRT1062/grblHAL_Teensy4/src/i2c.c#L339-L346

A big pity that the Teensy is not debuggable, makes it hard to develop for...

[terjeio]

Try with this code, it resets the bus and the I2C peripheral on a timeout. With this I can disconnect a signal to make the bus hang, after reconnect it starts working again.

void I2C_GetKeycode (uint32_t i2cAddr, keycode_callback_ptr callback)
{
    while(i2cIsBusy) {
        if(port->MSR & LPI2C_MSR_PLTF) {
            if(force_clock(hardware)) {
                port->MCR = LPI2C_MCR_RST;
                setClock(port, 100000);
            } else
                return; // or alarm?
        }
    }

    i2c.keycode_callback = callback;

    I2C_Receive(i2cAddr, NULL, 1, false);
}

[terjeio]

The bus reset code above has been added so I am closing this issue. Open a new at the new repo if still an issue.