Add a BME688 sensor

Makefile

@@ -14,7 +14,7 @@ RFM = 69
 LORA = 0
 
 MAIN = avr64ea.c
-SRC = rfm.c spi.c usart.c
+SRC = rfm.c spi.c usart.c bme68x/bme68x.c bme688.c
 
 CC = avr-gcc
 OBJCOPY = avr-objcopy
@@ -38,11 +38,13 @@ CFLAGS += -std=gnu99
 TARGET = $(strip $(basename $(MAIN)))
 SRC += $(TARGET).c
 SRC += ../librfm$(RFM)/librfm$(RFM).a
+SRC += ../bsec/AVR8_XMEGA/libalgobsec.a
 
 OBJ = $(SRC:.c=.o)
 OBJ = $(SRC:.S=.o)
 
-$(TARGET).elf: spi.h usart.h utils.h Makefile
+$(TARGET).elf: spi.h usart.h utils.h bme68x/bme68x.h bme68x/bme68x_defs.h \
+	bme688.h Makefile
 
 all: $(TARGET).hex
 

avr64ea.c

@@ -29,6 +29,7 @@
 #if RFM == 95
     #include "librfm95/librfm95.h"
 #endif
+#include "bme688.h"
 
 /* Timebase used for timing internal delays */
 #define TIMEBASE_VALUE ((uint8_t) ceil(F_CPU * 0.000001))
@@ -91,7 +92,7 @@ ISR(ADC0_RESRDY_vect) {
 EMPTY_INTERRUPT(ADC0_RESRDY_vect);
 
 /**
- * Radio module DIO and DIO4 (FSK)/DIO1 (LoRa) interrupt.
+ * Radio module DIO0 and DIO4 (FSK)/DIO1 (LoRa) interrupt.
  */
 ISR(PORTD_PORT_vect) {
     if (PORTD_INTFLAGS & PORT_INT_2_bm) {
@@ -134,6 +135,10 @@ static void initPins(void) {
     // PD1 is radio module CS pin (output pin + pullup)
     PORTD_DIRSET = (1 << PD1);
     PORTD_PIN1CTRL |= PORT_PULLUPEN_bm;
+
+    // PD2 is BME68x CS pin (output pin + pullup)
+    PORTD_DIRSET = (1 << PD2);
+    PORTD_PIN2CTRL |= PORT_PULLUPEN_bm;
 }
 
 /* Sets CPU and peripherals clock speed */
@@ -312,6 +317,12 @@ int main(void) {
         printString("Radio init failed!\r\n");
     }
 
+    int8_t bme688 = initBME68x();
+    if (bme688 < 0 && USART) {
+        printString("BME688 init failed!\r\n");
+        printInt(bme688);
+    }
+
     // enable global interrupts
     sei();
 

bme688.c

@@ -0,0 +1,144 @@
+/*
+ * File:   bme688.c
+ * Author: [email protected]
+ *
+ * Thanks to https://github.com/boschsensortec/BME68x_SensorAPI/tree/master/examples
+ *
+ * Created on 4. Oktober 2025, 20:31
+ */
+
+#include "bme688.h"
+
+/**
+ * Writes given register - data pairs to respective register(s).
+ *
+ * @param reg register of first register - data pair
+ * @param data array with data of first register - data pair as first element,
+ *   with remaining register - data pairs following
+ * @param len (number of register - data pairs) - 1
+ * @param intfPtr
+ * @return success
+ */
+static BME68X_INTF_RET_TYPE bme68xWrite(uint8_t reg,
+                                        const uint8_t *data,
+                                        uint32_t len,
+                                        void *intfPtr) {
+    PORTD_OUTCLR = (1 << PD4);
+    transmit(reg);
+    for (uint32_t i = 0; i < len; i++) {
+        transmit(data[i]);
+    }
+    PORTD_OUTSET = (1 << PD4);
+
+    // TODO
+    return 0;
+}
+
+/**
+ * Reads from register(s) into given data array starting with
+ * given register auto-incrementing.
+ *
+ * @param reg start register
+ * @param data array with data to be read from consecutive registers
+ * @param len number of registers to read from
+ * @param intfPtr
+ * @return success
+ */
+static BME68X_INTF_RET_TYPE bme68xRead(uint8_t reg,
+                                       uint8_t *data,
+                                       uint32_t len,
+                                       void *intfPtr) {
+    PORTD_OUTCLR = (1 << PD4);
+    transmit(reg);
+    for (uint32_t i = 0; i < len; i++) {
+        data[i] = transmit(0x00);
+    }
+    PORTD_OUTSET = (1 << PD4);
+
+    // TODO
+    return 0;
+}
+
+/**
+ * Delay function for BME68x - requires __DELAY_BACKWARD_COMPATIBLE__
+ * so delay does not have to be a compile time constant.
+ *
+ * @param period
+ * @param intfPtr
+ */
+static void bme68xDelayUs(uint32_t period, void *intfPtr) {
+    _delay_us(period);
+}
+
+int8_t initBME68x() {
+    struct bme68x_dev dev;
+    struct bme68x_conf conf;
+    struct bme68x_heatr_conf heater_conf;
+    struct bme68x_data data;
+    int8_t result;
+
+    uint8_t pin = PD4;
+
+    dev.intf = BME68X_SPI_INTF;
+    dev.write = bme68xWrite;
+    dev.read = bme68xRead;
+    dev.delay_us = bme68xDelayUs;
+    dev.intf_ptr = &pin; // TODO not used
+    dev.amb_temp = 20; // could use temp measured with thermistor ;-)
+
+    result = bme68x_init(&dev);
+    // TODO properly check result
+    if (result < 0) {
+        return result;
+    }
+
+    conf.filter = BME68X_FILTER_OFF;
+    conf.odr = BME68X_ODR_NONE;
+    conf.os_hum = BME68X_OS_8X;
+    conf.os_pres = BME68X_OS_8X;
+    conf.os_temp = BME68X_OS_8X;
+    result = bme68x_set_conf(&conf, &dev);
+    // TODO properly check result
+    if (result < 0) {
+        return result;
+    }
+
+    heater_conf.enable = BME68X_ENABLE;
+    heater_conf.heatr_temp = 300;
+    heater_conf.heatr_dur = 100;
+    result = bme68x_set_heatr_conf(BME68X_FORCED_MODE, &heater_conf, &dev);
+    // TODO properly check result
+    if (result < 0) {
+        return result;
+    }
+
+    result = bme68x_set_op_mode(BME68X_FORCED_MODE, &dev);
+    // TODO properly check result
+    if (result < 0) {
+        return result;
+    }
+
+    uint32_t meas_dur = bme68x_get_meas_dur(BME68X_FORCED_MODE, &conf, &dev) +
+            (heater_conf.heatr_dur * 1000);
+    dev.delay_us(meas_dur, dev.intf_ptr);
+
+    uint8_t n_data;
+    result = bme68x_get_data(BME68X_FORCED_MODE, &data, &n_data, &dev);
+    // TODO properly check result
+    if (result < 0) {
+        return result;
+    }
+
+    div_t tdiv = div(data.temperature, 100);
+
+    char buf[70];
+    snprintf(buf, sizeof (buf), "%c%d.%d°, %ld Pa, %ld %%, %ld Ohm, %d\r\n",
+            data.temperature < 0 ? '-' : ' ', abs(tdiv.quot), abs(tdiv.rem),
+            (uint32_t)data.pressure,
+            (uint32_t)(data.humidity / 1000),
+            (uint32_t)data.gas_resistance,
+            data.status);
+    printString(buf);
+
+    return true;
+}

bme688.h

@@ -0,0 +1,32 @@
+/* 
+ * File:   bme688.h
+ * Author: [email protected]
+ *
+ * Created on 4. Oktober 2025, 20:31
+ */
+
+#ifndef BME688_H
+#define BME688_H
+
+/* Allow passing a variable to _delay_* functions */
+#define __DELAY_BACKWARD_COMPATIBLE__
+
+#include <stdlib.h>
+#include <util/delay.h>
+
+#include "pins.h"
+#include "spi.h"
+#include "usart.h"
+#include "bme68x/bme68x.h"
+
+/**
+ * Initializes the BME68x sensor.
+ * 
+ * @return error code
+ */
+int8_t initBME68x(void);
+
+#undef __DELAY_BACKWARD_COMPATIBLE__
+
+#endif /* BME688_H */
+