W01 boot issue in environment with electromagnetic disturbance

[Angelo Di Franco]

Hi Everyone,
I have a problem with my own device based on Pycom W01 SoC.
Starting my device placed in a certain environment (A), it does not start.
If, on the other hand, I move it to another location (B), the device starts up correctly and continues to work properly.
Furthermore if once started in position B, I move it again to position A without turning it off or resetting it, the device continues to work correctly.
Probably the problem is due to an electromagnetic disturbance in position A which doesn’t allow to load the firmware in the right way.

The device has passed all the EMC tests, and it is CE marked.

Could you please help me to solve this problem?

Thank you in advance
Best regards

Angelo

[Andrea Picillo]

Hi Angelo. Have you tried to have a look to signals using an oscilloscope, paying more attention to power supply?
In my opinion there could be some problem in crystal trigger

[Angelo Di Franco]

This post is deleted!

[Angelo Di Franco]

@Andrea-Picillo Hi Andrea, thanks for your quick reply. What do you mean exactly with crystal trigger?

[Andrea Picillo]

@Angelo-Di-Franco I mean that maybe there aren't the best conditions to crystal/oscillators starting and you might not reach the needed frequency. That's only an idea. As I said before try to have a look to signals integrity, in particular way to power supply lines

[Angelo Di Franco]

@Andrea-Picillo Unfortunately, we cannot check the integrity of the power signals as the device is located at a customer.
We haven’t issued any problem on all the other devices in our laboratories, even on the power supply lines.
The crystal is inside the module W01 and therefore it should be shielded from EMC interferences by its own metal enclosure.
Is it possible that the interferences are picked up by the PIFA antenna printed on the PCB?
We are thinking as a possible solution to disable the WLAN in boot.py. What do you think about this?
Do you know which is the loading sequence of the three modules: pybytes, main.py and boot.py?

[Andrea Picillo]

@Angelo-Di-Franco The following code will help you:

pyexec_frozen_module("_boot.py");

    if (!soft_reset) {
    #if defined(GPY) || defined (FIPY)
        if(config_get_lte_modem_enable_on_boot())
        {
            //modlte_init0();
            // Notify the LTE thread to start
            //modlte_start_modem();
        }
    #endif
    }

    if (!safeboot) {
        // run boot.py
        int ret = pyexec_file("boot.py");
        if (ret & PYEXEC_FORCED_EXIT) {
            goto soft_reset_exit;
        }
        if (!ret) {
#ifndef RGB_LED_DISABLE
            // flash the system led
            mperror_signal_error();
#endif
        }
    }

    if (!safeboot) {
        // execute the frozen main first

#if (VARIANT == PYBYTES)
        if (config_get_pybytes_autostart()) {
            pyexec_frozen_module("_main_pybytes.py");
        } else {
        	pyexec_frozen_module("_main.py");
        }
#else
        pyexec_frozen_module("_main.py");
#endif

So the order is BOOT -> PYBYTES (if used) -> MAIN