How to use TRACE pins as GPIO

RE: How to use TRACE pins as GPIO

Matevz B — Tue, 23 Jun 2020 20:37:00 GMT

Thank you both TurboJ and hmolesworth for help and solving this issue.

I initially developed the application on nRF52 DK with nRF52832 where there was only P0. I was not aware of neat Nordic function, therefore I wrote my own. Switching to nRF52840 on custom PCB, use of P1 was more convenient, but obviously writing out of NRF_GPIO does no good.

I would only like to add a few things which I "figured out" (learnt actually) solving this issue. These may be useful for other newbies.

Nordic GPIO functions are defined in nrf_gpio.h.
There is also a function:
__STATIC_INLINE void nrf_gpio_pin_write(uint32_t pin_number, uint32_t value);
which can be used to "write" 0 and 1 (anything else actually).
NRF_CLOCK register is defined (among others) in nrf52840.h (or other corresponding file).

RE: How to use TRACE pins as GPIO

hmolesworth — Tue, 23 Jun 2020 02:00:21 GMT

Confusion between P0 and P1, easily done. NRF_GPIO refers to P0; better to either use all Nordic definitions or don't use any, but here they are mixed. Replace NRF_GPIO with NRF_P1 in this code, or just use the Nordic functions and not the NrF_GPIO and NRF_P1 registers directly. The function is (to set to '1') nrf_gpio_pin_set(pin) and so on.

RE: How to use TRACE pins as GPIO

Matevz B — Tue, 23 Jun 2020 00:24:25 GMT

Turbo J thank you.

It is set correct:
NRF_CLOCK->TRACECONFIG: 0x0

I added this:
__LOG(LOG_SRC_APP, LOG_LEVEL_INFO, "NRF_CLOCK->TRACECONFIG: 0x%x\n", NRF_CLOCK->TRACECONFIG);

Which resutls in:
main.c, 583, NRF_CLOCK->TRACECONFIG: 0x0

This is pin definition:
#define PIN_MOTOR_NEG NRF_GPIO_PIN_MAP(1,9)

This is pin configuration:
#define PIN_MOTOR_CONFIG ((GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos) | \
(GPIO_PIN_CNF_DRIVE_S0S1 << GPIO_PIN_CNF_DRIVE_Pos) | \
(GPIO_PIN_CNF_PULL_Disabled << GPIO_PIN_CNF_PULL_Pos) | \
(GPIO_PIN_CNF_INPUT_Disconnect << GPIO_PIN_CNF_INPUT_Pos) | \
(GPIO_PIN_CNF_DIR_Output << GPIO_PIN_CNF_DIR_Pos))

This is pin initialization:
gpio_pin_init(PIN_MOTOR_NEG, PIN_MOTOR_CONFIG);

The function:
void gpio_pin_init(uint32_t pin, uint32_t configuration)
{
NRF_GPIO->PIN_CNF[pin] = configuration;
}

Setting pin:
gpio_pin_set(PIN_MOTOR_NEG, 1);

Function:
void gpio_pin_set(uint32_t pin, uint8_t value)
{
if (value)
{
NRF_GPIO->OUTSET = 1UL << pin;
}
else
{
NRF_GPIO->OUTCLR = 1UL << pin;
}
}

And reading the pin immediatelly after setting returns 0.

The positive pin, P0.12 works fine with the same code.

RE: How to use TRACE pins as GPIO

Turbo J — Mon, 22 Jun 2020 23:51:06 GMT

Check the TRACECONFIG register (in CLOCK), e.g. with a debugger. Its contents shows whether the pins are GPIO or trace mode.