[auav] Robustify I2C transfers and enforce minimum sample time

src/drivers/differential_pressure/auav/AUAV.cpp

@@ -65,6 +65,7 @@ AUAV::AUAV(const I2CSPIDriverConfig &config) :
 	_sample_perf(perf_alloc(PC_ELAPSED, MODULE_NAME": read")),
 	_comms_errors(perf_alloc(PC_COUNT, MODULE_NAME": comms errors"))
 {
+	I2C::_retries = 5;
 }
 
 AUAV::~AUAV()
@@ -130,15 +131,21 @@ int AUAV::init()
 
 int AUAV::probe()
 {
-	uint8_t res_data = 0;
+	uint8_t res_data;
-	int status = transfer(nullptr, 0, &res_data, sizeof(res_data));
+
+	for (unsigned i = 0; i < 10; i++) {
+		res_data = 0;
+		int status = transfer(nullptr, 0, &res_data, 1);
 
 		/* Check that the sensor is active. Reported in bit 6 of the status byte */
-	if ((res_data & 0x40) == 0) {
+		if (status == PX4_OK && (res_data & 0x40)) {
-		status = PX4_ERROR;
+			return PX4_OK;
 		}
 
-	return status;
+		px4_usleep(10'000);
+	}
+
+	return PX4_ERROR;
 }
 
 void AUAV::handle_state_read_calibdata()

src/drivers/differential_pressure/auav/AUAV_Absolute.hpp

@@ -51,6 +51,8 @@ static constexpr uint8_t EEPROM_ABS_ES		= 0x38;
 /* Measurement rate is 50Hz */
 static constexpr unsigned ABS_MEAS_RATE = 50;
 static constexpr int64_t ABS_CONVERSION_INTERVAL = (1000000 / ABS_MEAS_RATE); /* microseconds */
+/* reading too fast can yield all zero data -> incorrect sensor reading */
+static_assert(ABS_CONVERSION_INTERVAL >= 7000, "Conversion interval is too fast");
 
 /* Conversions */
 static constexpr float MBAR_TO_PA = 100.0f;

src/drivers/differential_pressure/auav/AUAV_Differential.hpp

@@ -51,6 +51,8 @@ static constexpr uint8_t EEPROM_DIFF_ES		= 0x34;
 /* Measurement rate is 100Hz */
 static constexpr unsigned DIFF_MEAS_RATE = 100;
 static constexpr int64_t DIFF_CONVERSION_INTERVAL = (1000000 / DIFF_MEAS_RATE); /* microseconds */
+/* reading too fast can yield all zero data -> incorrect sensor reading */
+static_assert(DIFF_CONVERSION_INTERVAL >= 7000, "Conversion interval is too fast");
 
 /* Conversions */
 static constexpr float INH_TO_PA = 249.08f;