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Fix AK09918 init: correct WIA2 expected value and broken retry loop

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AK09918 WIA2 device ID is 0x0C (not 0x09 which belongs to AK09916).
Previous check falsely reported init failure for a working sensor.

The retry loop was resetting the sensor on every attempt, which clears
CNTL2 back to power-down before the sensor can produce a measurement.
At 100 Hz the first sample takes ~10 ms; checking isDataReady immediately
after switchMode always returned NOT_RDY, triggering another reset.

New approach: switch to continuous mode once, then poll with 15 ms
delay (one sample period + margin) up to 20 times without resetting.
Only re-apply the mode if an actual I2C read failure occurs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Josh
2026-04-23 22:38:05 +02:00
co-authored by Claude Sonnet 4.6
parent 2180415f5c
commit 12b025367c
1 changed files with 21 additions and 22 deletions
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IMU.cpp
+21 -22
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@@ -315,42 +315,41 @@ void imuInit()
if (qmi8658_.begin() == 0) if (qmi8658_.begin() == 0)
Serial.println("qmi8658_init fail"); Serial.println("qmi8658_init fail");
// Verify AK09918 is present on I2C before trying to configure it. // Verify AK09918 is present on I2C.
// WIA2 register (0x01) must return 0x09 on a real AK09918. // WIA1=0x48 (AKM company ID), WIA2=0x0C (AK09918 device ID).
{ {
const uint16_t devId = magnetometer_.getDeviceID(); const uint16_t devId = magnetometer_.getDeviceID();
const uint8_t wia1 = (uint8_t)(devId >> 8);
const uint8_t wia2 = (uint8_t)(devId & 0xFF); const uint8_t wia2 = (uint8_t)(devId & 0xFF);
if (wia2 != 0x09) { if (wia1 != 0x48 || wia2 != 0x0C) {
Serial.printf("AK09918_init fail: WIA2=0x%02X (expected 0x09). " Serial.printf("AK09918 warning: WIA1=0x%02X WIA2=0x%02X (expected 0x48/0x0C). "
"Check I2C wiring on SDA/SCL (GPIO32/33), " "Check I2C on SDA=GPIO32 SCL=GPIO33, address 0x0C.\n", wia1, wia2);
"address 0x0C, and power supply.\n", wia2);
} else { } else {
Serial.println("AK09918 found on I2C."); Serial.println("AK09918 found (WIA OK).");
} }
} }
// Initialize to power-down first so the subsequent switchMode goes through // Put sensor in a known state before switching to continuous mode.
// a defined state (unlike AK09918_NORMAL which skips I2C entirely).
magnetometer_.initialize(AK09918_POWER_DOWN); magnetometer_.initialize(AK09918_POWER_DOWN);
delay(1); delay(10); // datasheet: >=100µs after power-down; 10ms is safe
magnetometer_.switchMode(AK09918_CONTINUOUS_100HZ); magnetometer_.switchMode(AK09918_CONTINUOUS_100HZ);
err = magnetometer_.isDataReady();
int retry_times = 0; // At 100 Hz the first sample takes ~10 ms. Poll ST1 with a delay
while (err != AK09918_ERR_OK) { // instead of resetting on every attempt (reset clears the mode setting).
Serial.printf("AK09918 not ready (err=%d), retry %d/10...\n", err, retry_times + 1); err = AK09918_ERR_NOT_RDY;
delay(100); for (int retry_times = 0; retry_times < 20 && err != AK09918_ERR_OK; retry_times++) {
magnetometer_.reset(); delay(15); // wait one sample period (100Hz = 10ms) plus margin
delay(100);
magnetometer_.switchMode(AK09918_CONTINUOUS_100HZ);
err = magnetometer_.isDataReady(); err = magnetometer_.isDataReady();
retry_times ++; if (err == AK09918_ERR_READ_FAILED) {
if (retry_times > 10) { // I2C error – mode may have been lost, try re-applying it once.
Serial.println("AK09918 init timed out. Magnetometer will be unavailable."); Serial.printf("AK09918 I2C read failed on retry %d, re-applying mode...\n", retry_times + 1);
break; magnetometer_.switchMode(AK09918_CONTINUOUS_100HZ);
} }
} }
if (err == AK09918_ERR_OK) { if (err == AK09918_ERR_OK) {
Serial.println("AK09918 ready."); Serial.println("AK09918 ready.");
} else {
Serial.printf("AK09918 init timed out (last err=%d). Magnetometer will be unavailable.\n", err);
} }
// Serial.println("Start figure-8 calibration after 1 seconds."); // Serial.println("Start figure-8 calibration after 1 seconds.");
// delay(1000); // delay(1000);