Initial commit

SHTC3 comm via i2c works

code/nrf-connect/.gitignore

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+build

code/nrf-connect/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(hello_world)
+
+target_sources(app PRIVATE src/main.c src/prst/shtc3.c)

code/nrf-connect/nrf52840dk_nrf52840.overlay

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+// To get started, press Ctrl+Space (or Option+Esc) to bring up the completion menu and view the available nodes.
+
+// You can also use the buttons in the sidebar to perform actions on nodes.
+// Actions currently available include:
+
+// * Enabling / disabling the node
+// * Adding the bus to a bus
+// * Removing the node
+// * Connecting ADC channels
+
+// For more help, browse the DeviceTree documentation at https: //docs.zephyrproject.org/latest/guides/dts/index.html
+// You can also visit the nRF DeviceTree extension documentation at https: //nrfconnect.github.io/vscode-nrf-connect/devicetree/nrfdevicetree.html
+
+&pinctrl {
+	pwm0_default: pwm0_default {
+		group1 {
+			psels = <NRF_PSEL(PWM_OUT0, 0, 5)>;
+			nordic,invert;
+		};
+	};
+
+	pwm0_sleep: pwm0_sleep {
+		group1 {
+			psels = <NRF_PSEL(PWM_OUT0, 0, 5)>;
+			low-power-enable;
+		};
+	};
+
+	i2c0_default: i2c0_default {
+		group1 {
+			psels = <NRF_PSEL(TWIM_SDA, 0, 24)>,
+							<NRF_PSEL(TWIM_SCL, 0, 13)>;
+		};
+	};
+
+	i2c0_sleep: i2c0_sleep {
+		group1 {
+			psels = <NRF_PSEL(TWIM_SDA, 0, 24)>,
+							<NRF_PSEL(TWIM_SCL, 0, 13)>;
+			low-power-enable;
+		};
+	};
+};
+
+&i2c0 {
+	shtc3: shtc3@70 {
+		compatible = "i2c-device";
+		reg = <0x70>;
+		label = "SHTC3";
+	};
+};

code/nrf-connect/prj.conf

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+CONFIG_LOG=y
+CONFIG_CBPRINTF_FP_SUPPORT=y
+CONFIG_I2C=y

code/nrf-connect/src/main.c

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+#include <drivers/i2c.h>
+#include <logging/log.h>
+#include <zephyr/zephyr.h>
+
+#include "prst/shtc3.h"
+
+LOG_MODULE_REGISTER(main, LOG_LEVEL_DBG);
+
+void main(void) {
+  prst_shtc3_read_t shtc3_read = prst_shtc3_read();
+}

code/nrf-connect/src/prst/shtc3.c

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+#include "shtc3.h"
+
+#include <drivers/i2c.h>
+#include <logging/log.h>
+#include <zephyr/zephyr.h>
+
+LOG_MODULE_REGISTER(shtc3, LOG_LEVEL_DBG);
+
+static const struct i2c_dt_spec shtc3 = I2C_DT_SPEC_GET(DT_NODELABEL(shtc3));
+
+static uint8_t buff[6];
+
+static void write_cmd(uint16_t command) {
+  static uint8_t cmd[2];
+  cmd[0] = command >> 8;
+  cmd[1] = command & 0xff;
+  if (i2c_write_dt(&shtc3, cmd, sizeof(cmd)) != 0) {
+    LOG_ERR("Error writing command");
+  }
+}
+
+prst_shtc3_read_t prst_shtc3_read() {
+  // Wake the sensor up.
+  write_cmd(PRST_SHTC3_CMD_WAKEUP);
+  k_msleep(1);
+
+  // Request measurement.
+  write_cmd(PRST_SHTC3_CMD_MEASURE_TFIRST_NORMAL);
+
+  // Reading in normal (not low power) mode can take up to 12.1 ms, according to
+  // the datasheet.
+  k_msleep(15);
+
+  while (i2c_read_dt(&shtc3, buff, 6) != 0) {
+    k_msleep(10);
+  }
+
+  // Put the sensor in sleep mode.
+  write_cmd(PRST_SHTC3_CMD_SLEEP);
+
+  // TODO: Uninit i2c to save power?
+
+  // TODO: verify the CRC of the measurements. The function is described in the
+  // datasheet.
+
+  float temp_c = -45 + 175 * ((float)((buff[0] << 8) | buff[1])) / (1 << 16);
+  float humi = ((float)((buff[3] << 8) | buff[4])) / UINT16_MAX;
+
+  prst_shtc3_read_t ret = {.temp_c = temp_c, .rel_humi = humi};
+
+  LOG_INF("Read temp: %f oC (%d)", ret.temp_c, (int)temp_c);
+  LOG_INF("Read humi: %.0f %%", 100.0 * ret.rel_humi);
+  return ret;
+}

code/nrf-connect/src/prst/shtc3.h

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+#ifndef _PRST_SHT3C_H_
+#define _PRST_SHT3C_H_
+
+// Values from the SHTC3 datasheet.
+#define PRST_SHTC3_ADDR 0x70
+#define PRST_SHTC3_CMD_SLEEP 0xb098
+#define PRST_SHTC3_CMD_WAKEUP 0x3517
+#define PRST_SHTC3_CMD_MEASURE_TFIRST_LOW_POWER 0x609c
+#define PRST_SHTC3_CMD_MEASURE_TFIRST_NORMAL 0x7866
+
+typedef struct {
+  // Temperature in Celcius.
+  float temp_c;
+  // Relative humidity in [0, 1.0].
+  float rel_humi;
+} prst_shtc3_read_t;
+
+prst_shtc3_read_t prst_shtc3_read();
+
+#endif  // _PRST_SHT3C_H_