CC3220SF-LAUNCHXL: Device doesn't run if rx pin is in a low-level state

Mark81

Part Number: CC3220SF-LAUNCHXL
Other Parts Discussed in Thread: CC3220SF, CC3200

I'm facing a weird issue with a CC3220SF based board. For some reasons when the circuit is powered up it might happen that the rx pin (GPIO2, pin 57) is held down by an external device with a 1k resistor. Whenever this happens the CC3220SF doesn't run any code. If the logic level on that pin turns high and I reset the board it works as expected.

To narrow down the problem I created an extremely simple project (NoRTOS) that basically does the following:

int main(void)
{
    PRCMCC3200MCUInit();
    Power_init();
    NoRTOS_start();
    GPIO_init();
    GPIO_write(BOARD_GPIO_LED_RED, 1);

    return (0);
}

In this way I'm able to reproduce the problem. As you can see I didn't initialized the UART yet - anyway a 0V on the rx prevents the MCU to run.

Is there something obvious I'm missing about?

over 7 years ago

0 Hnz over 7 years ago

Guru 39650 points

Hi,

This is normal behaviour of CC3200 or CC3220 (see e2e.ti.com/.../2179292 ). Information how works SOP configuration and UART break you find at CC3220 datasheet at table 5-6.

Jan

0 Mark81 over 7 years ago in reply to Hnz

Expert 2610 points

Does the internal PowerCC32XX_WEAK_PULL_UP_STD setting in PowerCC32XX_ParkInfo is enough to guarantee the high-level state on startup or do I need an external pull-up resistor?

0 Jan D over 7 years ago in reply to Mark81

Guru 79905 points

Hi,

I suppose that external pull-up should be better. Because TX is scanned by ROM boatloader and your code is not executed before entering into bootloader. But as first thing you should check your SOP settings. Probably you are using this SOP settings [SOP2 - down, SOP1 - up, SOP0 - down], instead [SOP2 - down, SOP1 - down, SOP0 - down].

Jan

0 Mark81 over 7 years ago in reply to Jan D

Expert 2610 points

Yes, I'm using SOP010 as suggested in another thread some months ago. That was to avoid a dip-switch on the PCB.

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CC3220SF-LAUNCHXL: Device doesn't run if rx pin is in a low-level state