Zephyr sensors and MQTT - Arduino nano 33 BLE sense
This posts shows how the sensors on the Arduino nano 33 BLE sense can be used in Zephyr.
All files needed to build this program can be found at https://github.com/basaandewiel/zephyr_hts221_mqtt.
I tried to use sensors of my arduino, but found out that the sensors are not defined in the standard dts (device tree) file supplied for this board (in directory …zephyrprojects/zephyr/boards/arm/). After some searching I found this site https://devzone.nordicsemi.com/f/nordic-q-a/77845/problem-initializing-i2c-on-arduino-nano-33-ble.
It does not only provide an updated device tree with sensors, but also solved a bug in the initialization of the sensors.
The following device tree must be placed into ~/zephyrproject/zephyr/boards/arm/arduino_nano_33_ble
/*
* Copyright (c) 2020 Jefferson Lee
*
* SPDX-License-Identifier: Apache-2.0
*/
/dts-v1/;
#include <nordic/nrf52840_qiaa.dtsi>
/ {
model = "Arduino Nano 33 BLE (Sense)";
compatible = "arduino,arduino_nano_33_ble";
chosen {
zephyr,console = &uart0;
zephyr,shell-uart = &uart0;
zephyr,uart-mcumgr = &uart0;
zephyr,bt-mon-uart = &uart0;
zephyr,bt-c2h-uart = &uart0;
zephyr,sram = &sram0;
zephyr,flash = &flash0;
zephyr,code-partition = &code_partition;
};
leds {
compatible = "gpio-leds";
led0: led_0 {
gpios = <&gpio0 24 0>;
label = "Red LED";
};
led1: led_1 {
gpios = <&gpio0 16 0>;
label = "Green LED";
};
led2: led_2 {
gpios = <&gpio0 6 0>;
label = "Blue LED";
};
};
/* These aliases are provided for compatibility with samples */
aliases {
led0 = &led0;
1,1 Top
Following is also copied from the link mentioned above: Additionally, I changed zephyr/boards/arm/arduino_nano_33_ble/src/init_sensors.c such that initializing function is called at APPLICATION instead of PRE_KERNEL_1. Not sure why but initializing GPIO devices will cause the device to go fault at Pre_KERNEL_1.
/*
* Copyright (c) 2020 Jefferson Lee.
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <init.h>
#include <arduino_nano_33_ble.h>
/*
* this method roughly follows the steps here:
* https://github.com/arduino/ArduinoCore-nRF528x-mbedos/blob/6216632cc70271619ad43547c804dabb4afa4a00/variants/ARDUINO_NANO33BLE/variant.cpp#L136
*/
static int board_internal_sensors_init(const struct device *dev)
{
ARG_UNUSED(dev);
struct arduino_gpio_t gpios;
arduino_gpio_init(&gpios);
arduino_gpio_pinMode(&gpios, ARDUINO_LEDPWR, GPIO_OUTPUT);
arduino_gpio_digitalWrite(&gpios, ARDUINO_LEDPWR, 1);
CoreDebug->DEMCR = 0;
NRF_CLOCK->TRACECONFIG = 0;
/*
* Arduino uses software to disable RTC1,
* but I disabled it using DeviceTree
*/
/* nrf_rtc_event_disable(NRF_RTC1, NRF_RTC_INT_COMPARE0_MASK); */
/* nrf_rtc_int_disable(NRF_RTC1, NRF_RTC_INT_COMPARE0_MASK); */
NRF_PWM_Type * PWM[] = {
NRF_PWM0, NRF_PWM1, NRF_PWM2, NRF_PWM3
};
for (unsigned int i = 0; i < (ARRAY_SIZE(PWM)); i++) {
PWM[i]->ENABLE = 0;
PWM[i]->PSEL.OUT[0] = 0xFFFFFFFFUL;
}
/*
* the PCB designers decided to use GPIO's
* as power pins for the internal sensors
*/
arduino_gpio_pinMode(&gpios, ARDUINO_INTERNAL_VDD_ENV_ENABLE, GPIO_OUTPUT);
arduino_gpio_pinMode(&gpios, ARDUINO_INTERNAL_I2C_PULLUP, GPIO_OUTPUT);
arduino_gpio_digitalWrite(&gpios, ARDUINO_INTERNAL_VDD_ENV_ENABLE, 1);
arduino_gpio_digitalWrite(&gpios, ARDUINO_INTERNAL_I2C_PULLUP, 1);
return 0;
}
SYS_INIT(board_internal_sensors_init, APPLICATION, 32);
First of all I wanted to test whether the sensors are working; so I initialised the temperature and humidity sensors and printed their values to the console. The following program is working, but during the first boot the sensors are sometimes not recognized; after a reboot it is always working; I do not yet know why the behaviour after the first boot is not correct.
/*
* Copyright (c) 2017 Linaro Limited
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <zephyr.h>
#include <device.h>
#include <drivers/sensor.h>
#include <stdio.h>
#include <sys/util.h>
#include <sys/printk.h>
#include <usb/usb_device.h>
#include <drivers/uart.h>
const struct device *dev;
static void process_sample(const struct device *dev)
{
struct sensor_value temp, hum;
if (sensor_sample_fetch(dev) < 0) {
printk("Sensor sample update error\n");
return;
}
if (sensor_channel_get(dev, SENSOR_CHAN_AMBIENT_TEMP, &temp) < 0) {
printk("Cannot read HTS221 temperature channel\n");
return;
}
if (sensor_channel_get(dev, SENSOR_CHAN_HUMIDITY, &hum) < 0) {
printk("Cannot read HTS221 humidity channel\n");
return;
}
/* display temperature */
printk("Temperature:%.1f C\n", sensor_value_to_double(&temp));
/* display humidity */
printk("Relative Humidity:%.1f%%\n",
sensor_value_to_double(&hum));
}
void init_usb_serial(void) {
uint32_t dtr = 0;
if (usb_enable(NULL)) {
return;
}
/* Poll if the DTR flag was set */
dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_console));
while (!dtr) {
uart_line_ctrl_get(dev, UART_LINE_CTRL_DTR, &dtr);
/* Give CPU resources to low priority threads. */
k_sleep(K_MSEC(100));
}
k_sleep(K_MSEC(5000)); //give user time to start 'screen /dev/ttyACM0'
}
void main(void)
{
init_usb_serial(); //so we can printk to console
dev = device_get_binding("HTS221"); //string must match string in device tree
//dev = device_get_binding(DT_LABEL(DT_INST(0, st_hts221)));
if (dev == NULL) {
printk("Could not get HTS221 device\n");
return;
}
while (true) {
process_sample(dev);
k_sleep(K_MSEC(2000));
}
}
The MQTT part will be added soon.