Thingy91 accessing P6 GPIO of nrf52840

RE: Thingy91 accessing P6 GPIO of nrf52840

JCampa — Wed, 03 Nov 2021 21:02:11 GMT

I found out how to read the voltage level on TP32, and logical level on TP33, which is enough for my purposes.

For anyone wondering how to do it:

TP32 is AIN0 and TP33 is AIN3 for the Thingy91 (https://infocenter.nordicsemi.com/topic/ug_thingy91/UG/thingy91/hw_description/pin_maps.html)

So using the Analog Digital Converter (ADC) sample code found here: fw-nrfconnect-nrf/main.c at nrf9160_samples · Rallare/fw-nrfconnect-nrf (github.com)

Modifying this to make it useable (lot of old libraries that have been moved):

/*
 * Copyright (c) 2018 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-BSD-5-Clause-Nordic
 */

#include <net/socket.h>
#include <nrf9160.h>
#include <stdio.h>
#include <string.h>
#include <drivers/uart.h>
#include <drivers/adc.h>
#include <zephyr.h>

//variables needed for ADC channel reading
struct device *adc_dev;
#define BUFFER_SIZE 1
static uint16_t m_sample_buffer[BUFFER_SIZE];

//Setting needed ADC settings
#if defined(CONFIG_BOARD_NRF9160DK_NRF9160_NS)	|| \
	defined(CONFIG_BOARD_THINGY91_NRF9160_NS)
#include <hal/nrf_saadc.h>
#define ADC_DEVICE_NAME DT_ADC_0_NAME
#define ADC_RESOLUTION 10
#define ADC_GAIN ADC_GAIN_1_6
#define ADC_REFERENCE ADC_REF_INTERNAL
#define ADC_ACQUISITION_TIME ADC_ACQ_TIME(ADC_ACQ_TIME_MICROSECONDS, 10)
#define ADC_1ST_CHANNEL_ID 0
#define ADC_1ST_CHANNEL_INPUT NRF_SAADC_INPUT_AIN0

#endif

static const struct adc_channel_cfg m_1st_channel_cfg = {
	.gain = ADC_GAIN,
	.reference = ADC_REFERENCE,
	.acquisition_time = ADC_ACQUISITION_TIME,
	.channel_id = ADC_1ST_CHANNEL_ID,
#if defined(CONFIG_ADC_CONFIGURABLE_INPUTS)
	.input_positive = ADC_1ST_CHANNEL_INPUT,
#endif
};

static int adc_sample(void)
{
	int ret;

	const struct adc_sequence sequence = {
		.channels = BIT(ADC_1ST_CHANNEL_ID),
		.buffer = m_sample_buffer,
		.buffer_size = sizeof(m_sample_buffer),
		.resolution = ADC_RESOLUTION,
	};

	if (!adc_dev) {
		return -1;
	}

	ret = adc_read(adc_dev, &sequence);
	if (ret < 0) {
		printk("ADC read err: %d\n", ret);
		return ret;
	}
	/* Print the AIN0 values */
		float adc_voltage = 0;
		adc_voltage = (float)(((float)m_sample_buffer[0] / 1023.0f) *
				      3600.0f);
		printk("ADC raw value: %d\n", m_sample_buffer[0]);
		printf("Measured voltage: %f mV\n", adc_voltage);

	return ret;
}

int main(void)
{
	int err;

	printk("nrf91 saadc sampling AIN0 (P0.13)\n");
	printk("Example requires secure_boot to have ");
	printk("SAADC set to non-secure!\n");
	printk("If not; BusFault/UsageFault will be triggered\n");

	adc_dev = device_get_binding("ADC_0");
	if (!adc_dev) {
		printk("device_get_binding ADC_0 failed\n");
	}
	err = adc_channel_setup(adc_dev, &m_1st_channel_cfg);
	if (err) {
		printk("Error in adc setup: %d\n", err);
	}

	/* Trigger offset calibration
	 * As this generates a _DONE and _RESULT event
	 * the first result will be incorrect. 
	 */
	NRF_SAADC_NS->TASKS_CALIBRATEOFFSET = 1;
	while (1) {
		//380 - 176 range
		err = adc_sample();
		if (err) {
			printk("Error in adc sampling: %d\n", err);
		}
		k_sleep(K_MSEC(500));
	}
}

Your project config file should include (at least):

CONFIG_ADC=y
CONFIG_ADC_ASYNC=y
CONFIG_NRFX_SAADC=y
CONFIG_NEWLIB_LIBC_FLOAT_PRINTF=y
CONFIG_NEWLIB_LIBC=y

You can flash this to the Thingy:91 (I used the DK and JTAG cable method, don't know if the MCUBoot one would work or not) and connect whatever input voltage you are trying to read to TP32 which is right above Switch 3 on the PCB.

Additionally, if all you need is the logical level you can use pins 13 and 16 to connect to Test Points 32 and 33 respectively.

I hope this helps others like me who are newer to this, as I find having simple examples to build off of is very helpful!

-Julian

RE: Thingy91 accessing P6 GPIO of nrf52840

JCampa — Tue, 02 Nov 2021 14:05:17 GMT

Hi, thanks for telling us about the modified Connectivity Bridge firmware need, could you explain further what exactly has to be modified, as the CONFIG_GPIO is already set to y and I can't see anything else that would be relevant?

Yes it was the SENSE_LED - the Port 0 Pin 1 explanation seems right to me.

One of the sensors needs power/GND/Analog input, while the other sensor just needs power/Analog input. The power and GND connections will be done with connector P5 (the 3.3V and GND connections).

Really all I need to do is read the analog voltage on two of the 6 pins on P6 or the test points 32 and 33. I am able to read the logical level on the test points, however I really need the actual voltage on the point. Is there a way to get the actual voltage level from pin reads?

Those two tickets you linked were helpful, thanks!

RE: Thingy91 accessing P6 GPIO of nrf52840

helsing — Mon, 01 Nov 2021 21:48:53 GMT

Hello Julian,

If you would like to use the pins on P6 you would need to program nRF52840 with a modified version of the Connectivity Bridge firmware. Remember to set the switch to nRF52 on the Thingy when programming the 52 device.

Why did you see a green light?

NRF_GPIO_PIN_MAP is provided to reference the ports and pins on the IC, not the ports and pins on Thingy:91. Which LED goes green, the SENSE_LED or the lightwell?

If it is the SENSE_LED that goes green then I suppose the explanation could be that this result after the use of the macro is port 0, pin 1(P0.01) on nRF9160.

Thingy91 accessing P6 GPIO of nrf52840

RE: Thingy91 accessing P6 GPIO of nrf52840

RE: Thingy91 accessing P6 GPIO of nrf52840

RE: Thingy91 accessing P6 GPIO of nrf52840

Why did you see a green light?

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