Update driver code to accept point to application delay function

Updates the driver code to accept a function point to a delay function
determined by the application. This allows the application to determine
the delay implementation, for example, using a hardware timer.

Also updates the test application to use new functionality.

Author: nkanderson

libs/bme68x/Inc/bme68x_driver.h

@@ -90,7 +90,7 @@ typedef struct
  * @param[in,out] bme Pointer to newly initialized bme68x sensor interface
  * @param[in] i2c_handle Pointer to I2C handle.
  */
-void bme_init(bme68x_sensor_t *bme, I2C_HandleTypeDef *i2c_handle);
+void bme_init(bme68x_sensor_t *bme, I2C_HandleTypeDef *i2c_handle, bme68x_delay_us_fptr_t delay_fn);
 
 /**
  * @brief Returns basic status check
@@ -175,18 +175,6 @@ uint8_t bme_fetch_data(bme68x_sensor_t *bme);
  */
 uint32_t bme_get_meas_dur(bme68x_sensor_t *bme, uint8_t opmode);
 
-/**
- * @brief Implements the default microsecond delay callback
- *
- * Sets the delay_us function pointer on the bme68x_dev device struct.
- * This callback is used throughout the Bosch library whenever a microsecond
- * delay is necessary for proper device functioning.
- *
- * @param[in] period_us Duration of the delay in microseconds
- * @param[in] intf_ptr Pointer to the interface descriptor
- */
-void bme_delay_us(uint32_t period_us, void *intf_ptr);
-
 /**
  * @brief Implements the default I2C write transaction
  *

libs/bme68x/Src/bme68x_driver.c

@@ -16,7 +16,7 @@
 /* ========================== FUNCTION IMPLEMENTATIONS ========================== */
 
 /** Initializes the BME68x sensor interface */
-void bme_init(bme68x_sensor_t *bme, I2C_HandleTypeDef *i2c_handle)
+void bme_init(bme68x_sensor_t *bme, I2C_HandleTypeDef *i2c_handle, bme68x_delay_us_fptr_t delay_fn)
 {
   if (bme == NULL)
   {
@@ -36,7 +36,7 @@ void bme_init(bme68x_sensor_t *bme, I2C_HandleTypeDef *i2c_handle)
   /** @todo (maybe) Assign variant ID on bme struct */
   bme->device.read = &bme_read;
   bme->device.write = &bme_write;
-  bme->device.delay_us = bme_delay_us;
+  bme->device.delay_us = delay_fn;
   bme->status = BME68X_OK;
   // Typical ambient temperature in Celsius
   bme->device.amb_temp = 25;
@@ -119,21 +119,6 @@ uint32_t bme_get_meas_dur(bme68x_sensor_t *bme, uint8_t opmode)
   return bme68x_get_meas_dur(opmode, &bme->conf, &bme->device);
 }
 
-/** Implements the default microsecond delay callback */
-void bme_delay_us(uint32_t period_us, void *intf_ptr)
-{
-  // intf_ptr is not used, but it is part of the standard function signature
-  // so cast to void to avoid compiler warning
-  (void)intf_ptr;
-  /** @todo: Implement a microsecond delay here, possibly with a DWT cycle counter, or an actual hardware timer */
-  // FIXME: Short-term implementation of a blocking delay
-  volatile uint32_t cycles = period_us * 20;
-  while (cycles--)
-  {
-    __NOP();
-  }
-}
-
 /** Implements the default microsecond delay callback */
 int8_t bme_write(uint8_t reg_addr, const uint8_t *reg_data, uint32_t length, void *intf_ptr)
 {

targets/stm32L4xx/L476RG/Src/tim.c

@@ -113,6 +113,7 @@ void HAL_TIM_Base_MspDeInit(TIM_HandleTypeDef* tim_baseHandle)
 /** Example implementation for a microsecond delay callback */
 void delay_us_timer(uint32_t us, void *intf_ptr)
 {
+  (void)intf_ptr;
   /* Reset completion flag */
   delay_complete = 0;
 

tests/test_bme688/test_bme688.c

@@ -109,7 +109,7 @@ int main(void)
 
   // Create bme interface struct and initialize it
   bme68x_sensor_t bme;
-  bme_init(&bme, &hi2c1);
+  bme_init(&bme, &hi2c1, &delay_us_timer);
   // Check status, should be 0 for OK
   int bme_status = bme_check_status(&bme);
   {
@@ -145,7 +145,7 @@ int main(void)
     // Set to forced mode, which takes a single sample and returns to sleep mode
     bme_set_opmode(&bme, BME68X_FORCED_MODE);
     /** @todo: May adjust the specific timing function called here, but it should be based on bme_get_meas_dur */
-    bme_delay_us(bme_get_meas_dur(&bme, BME68X_SLEEP_MODE), &hi2c1);
+    delay_us_timer(bme_get_meas_dur(&bme, BME68X_SLEEP_MODE), &hi2c1);
     // Fetch data
     int fetch_success = bme_fetch_data(&bme);
     if (fetch_success)