Using UARTE1 as event line

[Malcolm]

I am interfacing nRF to a GPRS modem. In order to ensure the modem is in a known state I do a power cycle of the modem and I determine completion by monitoring the TX line from the modem using the UARTE1 RX. When the modem powers down the modem TX line goes low, and when the modem completes it power up the modem TX line goes high ready to act as UART.

I would like to detect the change from low to high in the modem TX line as an event through the UARTE1 line before enabling as a uart.

I can monitor the change successfully by polling the UARTE1 RX line, but I am trying to make this as an event.

I have followed the example for the on board switch of the dongle, which functions.

I have as code

#define UARTE1_RX_PIN 17    /* (P0.17) */

#define POWER_ON_PIN    UARTE1_RX_PIN    /* (P0.17)*/

                        nrf_drv_gpiote_in_config_t in_config = NRFX_GPIOTE_CONFIG_IN_SENSE_LOTOHI(false);
                        err_code = nrf_drv_gpiote_in_init(POWER_ON_PIN, &in_config, gprsTurnOnTxHighHandler);
                        APP_ERROR_CHECK(err_code);
                        nrf_drv_gpiote_in_event_enable(POWER_ON_PIN,true);

However I never see an interrupt

I am using SDK16.0

[Einar Thorsrud]

Hi,

Did you disable the UART first? If not, this will not work (you cannot use a pin as GPIO and a UART pin at the same time).

[Malcolm]

I do not enable as a UART until I see the line go high once the modem has initialised.

Currently this works in polling mode; I set a timer that polls the line every 100ms and this works so it is acting as input.

[Einar Thorsrud]

I see. I do not immediately spot any issues in the code snippet you have here though, and it should work. You can refer to the pin change interrupt example in the SDK. That would be more or less equivalent with that you have here except that it triggers on both high and low and use GPIOTE (high accuracy, at the expense of current consumption). But if you change the configuration to the input pin from PIOTE_CONFIG_IN_SENSE_TOGGLE(false) to NRFX_GPIOTE_CONFIG_IN_SENSE_LOTOHI(false) the example still works and demonstrate what you need.

[Malcolm]

This snippet is buried in 1000's of lines of code so anything could be happening. I am going to strip this back and replace the switch line for the UARTE1 RX line and use a jumper as switch. If that works I will move forward.

[Malcolm]

I went to the sample you suggested and followed the code. I have determined the issue.

I am configuring 2 interrupt lines but

#define NRFX_GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS 1

whereas 8 are configure for high power

[Malcolm]

I changed the number of events and I can generate interupt on both lines, including UARTE1 RX line, so that indicates the interrupt mechansm is work.

My software has 4 events defined and I configure only 2 so this is not my issue. I will investigate further.

[Einar Thorsrud]

Hi,

You should get a no mem error returned from nrf_drv_gpiote_in_init() the problem is that you have configured too few low power events, so it makes sense that it is not the issue. Even so, please note that GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS will be used, and not NRFX_GPIOTE_CONFIG_NUM_OF_LOW_POWER_EVENTS (generally, the nrfx configurations are not used - see doc for details).