STM32WL I2C not working in Release, no issue in Debug/Develop

[hallard]

Description of defect

Working with ATECC I2C device for LoRa, in Debug or Develop mode works like a charm, as soon as I build in Release mode, device is not seen anymore and can't talk with it. Everything else is working fine (LoRaWAN and app job)

Tried basic I2C scanner, same thing, device is not seen building Release

Target(s) affected by this defect ?

STM32WL LoRa-E5 (may be other)

Toolchain(s) (name and version) displaying this defect ?

What version of Mbed-os are you using (tag or sha) ?

6.14 6.15.1 master

What version(s) of tools are you using. List all that apply (E.g. mbed-cli)

Mbed Studio

How is this defect reproduced ?

Switch Build profile to Debug, Release or Develop

[jeromecoutant]

Hi Only 2 difference between release and develop profile...

• NDEBUG (only in release)
• MBED_TRAP_ERRORS_ENABLED=1 (only in develop)

[hallard]

I just split off I2C stuff onto a basic program just to be sure, can't be easier, in the same time I wired a 2nd IC2 device on same bus (9 DoF sensor)

#include "mbed.h"

I2C i2c(PA_15, PB_15); 

int main(void)
{
    printf("\n***** I2C Scanner *****\n");
        ThisThread::sleep_for(2s);

    int count = 0;
    for (int address = 0; address < 127; address++) {
        if (!i2c.write(address << 1, NULL, 0)) {                                                                                                  
            printf("I2C device found at address 0x%02x (8-bits 0x%02X)\n", address, address << 1);
            count++;
        }
        ThisThread::sleep_for(20ms);
    }
    printf("%d device(s) found\n", count);
}

debug output

***** I2C Scanner *****
I2C device found at address 0x58 (8-bits 0xB0)
I2C device found at address 0x69 (8-bits 0xD2)
2 device(s) found

develop output

***** I2C Scanner *****
I2C device found at address 0x58 (8-bits 0xB0)
I2C device found at address 0x69 (8-bits 0xD2)
2 device(s) found

release output

***** I2C Scanner *****
I2C device found at address 0x69 (8-bits 0xD2)
1 device(s) found

and as final test just to be sure, I switched 9Dof Sensor with a 2nd ATECC608 (adafruit stema board)

Develop output

***** I2C Scanner *****
I2C device found at address 0x58 (8-bits 0xB0)
I2C device found at address 0x60 (8-bits 0xC0)
2 device(s) found

Release output

***** I2C Scanner *****
0 device(s) found

Not sure what's going on on I2C stuff in release mode, looks like ATECC does not answer in release, would love to know results of this piece of code if anyone has a board with ATECC chip

[jeromecoutant]

Does it change something if i2c is not global ?

[hallard]

Nope, I tried also just in case, forgot to mention

[hallard]

Ok got some investigations and found the root cause, it's ATECC Secure Element, I discovered sometime I need to scan I2C bus with some device addresses before to get the device seen. So I tried to detect the device several time to see it.

#include "mbed.h"
I2C i2c(PA_15, PB_15); // SDA, SCL
int main(void)
{
    int i, address;
    printf("\n***** I2C Scanner *****\n");
    i2c.frequency(100000);
    ThisThread::sleep_for(1s);

    address = 0x58;                                                                                          
    printf("I2C Check address 0x%02x (8-bits 0x%02X) => ", address, address << 1);
    for (i=0; i<8; i++) {
        if (!i2c.write(address << 1, NULL, 0)) {
            printf("Found after %d queries\n", i+1);
            return 0;
        }
        ThisThread::sleep_for(2ms);
    }
    printf("Not found after %d queries\n", i+1);
}

When running in Develop or Debug sometime it is seen after 2 queries other 6 or 8.

And reading around seen some send 4 x 00 on I2C bus at 100KHz to wakeup the device (this pull SDA low enough time to wake the device), Yes, because it need to be waked pulling SDA line low for sometime.

So I dirty fixed like that and no more problem

#include "mbed.h"
I2C i2c(PA_15, PB_15); // SDA, SCL
int main(void)
{
    int i, address;
    printf("\n***** I2C Scanner *****\n");
    i2c.frequency(100000);
    ThisThread::sleep_for(1s);
    // Force ATECC to wake up then deinstantiate  DigitalOut
    {
        DigitalOut sda(PA_15);
        sda = 0;
        ThisThread::sleep_for(10ms);
        sda = 1;
        ThisThread::sleep_for(2ms); // Let time to wake up
    }

    address = 0x58;                                                                                      
    printf("I2C Check address 0x%02x (8-bits 0x%02X) => ", address, address << 1);
    if (!i2c.write(address << 1, NULL, 0)) {
        printf("Found\n");
    } else 
        printf("Not Found\n");
    }
}

With this dirty fix it works in Release and all mode. But the deal is that using mbed-CryptoAuthLib and CryptoAuthLib has the same issue, so in my code I needed to wake up every time I call crypto function that call atcab_init()(because I like to put device into sleep after use calling atcab_release();

So I don't know who's guru in charge of that but this means official examples mbed-os-example-atecc608a does not works either in 'Release'. I will open issue on this one.