calibrated with two 2 minute rotation logs of upright and sideways

exercises/22_compass/scripts/calc_mag_offsets.py

@@ -0,0 +1,134 @@
+#!/usr/bin/env python3
+
+from __future__ import annotations
+
+import argparse
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Iterable
+
+
+@dataclass
+class AxisStats:
+    min_value: int | None = None
+    max_value: int | None = None
+
+    def update(self, value: int) -> None:
+        if self.min_value is None or value < self.min_value:
+            self.min_value = value
+        if self.max_value is None or value > self.max_value:
+            self.max_value = value
+
+    @property
+    def offset(self) -> float:
+        assert self.min_value is not None and self.max_value is not None
+        return (self.min_value + self.max_value) / 2.0
+
+    @property
+    def span(self) -> int:
+        assert self.min_value is not None and self.max_value is not None
+        return self.max_value - self.min_value
+
+
+@dataclass
+class FileStats:
+    sample_count: int
+    x: AxisStats
+    y: AxisStats
+    z: AxisStats
+
+
+def parse_log(path: Path) -> FileStats:
+    x = AxisStats()
+    y = AxisStats()
+    z = AxisStats()
+    sample_count = 0
+
+    with path.open("r", encoding="utf-8") as handle:
+        for raw_line in handle:
+            line = raw_line.strip()
+            if not line or line.startswith("#"):
+                continue
+            fields = line.split("\t")
+            if len(fields) < 13:
+                continue
+            x.update(int(fields[4]))
+            y.update(int(fields[5]))
+            z.update(int(fields[6]))
+            sample_count += 1
+
+    if sample_count == 0:
+        raise ValueError(f"{path}: no samples found")
+
+    return FileStats(sample_count=sample_count, x=x, y=y, z=z)
+
+
+def merge_stats(items: Iterable[FileStats]) -> FileStats:
+    merged = FileStats(sample_count=0, x=AxisStats(), y=AxisStats(), z=AxisStats())
+    for item in items:
+        merged.sample_count += item.sample_count
+        merged.x.update(item.x.min_value)
+        merged.x.update(item.x.max_value)
+        merged.y.update(item.y.min_value)
+        merged.y.update(item.y.max_value)
+        merged.z.update(item.z.min_value)
+        merged.z.update(item.z.max_value)
+    return merged
+
+
+def print_stats(label: str, stats: FileStats) -> None:
+    print(f"{label}:")
+    print(f"  samples={stats.sample_count}")
+    print(
+        f"  raw_x min={stats.x.min_value} max={stats.x.max_value} "
+        f"offset={stats.x.offset:.1f} span={stats.x.span}"
+    )
+    print(
+        f"  raw_y min={stats.y.min_value} max={stats.y.max_value} "
+        f"offset={stats.y.offset:.1f} span={stats.y.span}"
+    )
+    print(
+        f"  raw_z min={stats.z.min_value} max={stats.z.max_value} "
+        f"offset={stats.z.offset:.1f} span={stats.z.span}"
+    )
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Compute raw magnetometer midpoint offsets from one or more log files.")
+    parser.add_argument("logs", nargs="+", help="Magnetometer log file(s)")
+    parser.add_argument("--prior-x", type=float, default=0.0, help="Previously compiled raw X offset")
+    parser.add_argument("--prior-y", type=float, default=0.0, help="Previously compiled raw Y offset")
+    parser.add_argument("--prior-z", type=float, default=0.0, help="Previously compiled raw Z offset")
+    args = parser.parse_args()
+
+    per_file: list[tuple[Path, FileStats]] = []
+    for item in args.logs:
+        path = Path(item)
+        per_file.append((path, parse_log(path)))
+
+    for path, stats in per_file:
+        print_stats(path.name, stats)
+
+    if len(per_file) > 1:
+        print()
+
+    combined = merge_stats(stats for _, stats in per_file)
+    print_stats("combined", combined)
+
+    print()
+    print("residual_offsets:")
+    print(f"  x={combined.x.offset:.1f}")
+    print(f"  y={combined.y.offset:.1f}")
+    print(f"  z={combined.z.offset:.1f}")
+
+    print()
+    print("updated_total_offsets:")
+    print(f"  x={args.prior_x + combined.x.offset:.1f}")
+    print(f"  y={args.prior_y + combined.y.offset:.1f}")
+    print(f"  z={args.prior_z + combined.z.offset:.1f}")
+
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())

exercises/22_compass/src/main.cpp

@@ -61,6 +61,9 @@ static constexpr uint8_t kMagCandidateCount = 3;
 static constexpr uint8_t kMagCandidates[kMagCandidateCount] = {0x1C, 0x3C, 0x0D};
 static constexpr float kDeclinationDeg = MAG_DECLINATION_DEG;
 static constexpr float kDegPerRad = 57.29577951308232f;
+static constexpr float kMagOffsetRawX = -7993.0f;
+static constexpr float kMagOffsetRawY = 4608.0f;
+static constexpr float kMagOffsetRawZ = 3456.0f;
 
 
 struct ClockDateTime {
@@ -385,32 +388,6 @@ void handleWebDownload() {
   file.close();
 }
 
-void startWebServerOLD() {
-  // GPSQA-CY is a carry-over from previous exercises, but we can keep the SSID for continuity. 
-  //The unique board ID is in the suffix, and the IP address is fixed based on LOG_AP_IP_OCTET.
-  snprintf(g_apSsid, sizeof(g_apSsid), "GPSQA-%s", kBoardId);
-  WiFi.mode(WIFI_AP);
-  WiFi.setSleep(false);
-  const IPAddress ip(192, 168, LOG_AP_IP_OCTET, 1);
-  const IPAddress gw(192, 168, LOG_AP_IP_OCTET, 1);
-  const IPAddress nm(255, 255, 255, 0);
-  WiFi.softAPConfig(ip, gw, nm);
-  // no password required.
-  if (!WiFi.softAP(g_apSsid)) {
-    Serial.println("wifi_ap=failed");
-    return;
-  }
-  Serial.println("wifi_ap=started");
-  g_server.on("/", HTTP_GET, handleWebIndex);
-  g_server.on("/files", HTTP_GET, handleWebFiles);
-  g_server.on("/download", HTTP_GET, handleWebDownload);
-  g_server.begin();
-  g_webReady = true;
-
-  Serial.printf("wifi_ap_ssid=%s\n", g_apSsid);
-  Serial.printf("wifi_ap_url=http://192.168.%u.1/\n", (unsigned)LOG_AP_IP_OCTET);
-}
-
 void startWebServer() {
   // GPSQA-CY is a carry-over from previous exercises, but we can keep the SSID for continuity. 
   //The unique board ID is in the suffix, and the IP address is fixed based on LOG_AP_IP_OCTET.
@@ -518,7 +495,12 @@ bool initMagnetometer() {
       SensorQMC6310::DATARATE_200HZ,
       SensorQMC6310::OSR_1,
       SensorQMC6310::DSR_1);
-  return rc == 0;
+  if (rc != 0) {
+    return false;
+  }
+
+  g_qmc.setOffset(kMagOffsetRawX, kMagOffsetRawY, kMagOffsetRawZ);
+  return true;
 }
 
 bool mountSd() {
@@ -699,6 +681,7 @@ void printBootSummary() {
   Serial.printf("oled_wire_pins=sda:%d scl:%d addr:0x%02X\n", OLED_SDA, OLED_SCL, OLED_ADDR);
   Serial.printf("declination_deg=%.2f\n", kDeclinationDeg);
   Serial.printf("sample_interval_ms=%lu\n", (unsigned long)kSampleIntervalMs);
+  Serial.printf("mag_offsets_raw=%.1f,%.1f,%.1f\n", kMagOffsetRawX, kMagOffsetRawY, kMagOffsetRawZ);
 }
 
 void appSetup() {
@@ -747,6 +730,7 @@ void appSetup() {
   }
 
   Serial.printf("magnetometer_init=ok label=%s addr=0x%02X chip=0x%02X\n", g_magLabel, g_magAddress, g_magChipId);
+  Serial.printf("magnetometer_offsets_applied=%.1f,%.1f,%.1f\n", kMagOffsetRawX, kMagOffsetRawY, kMagOffsetRawZ);
 
   if (g_timeValid && g_sdMounted) {
     if (openLogFile()) {
@@ -762,7 +746,7 @@ void appSetup() {
 
   startWebServer();
 
-  drawLines("Exercise 22", "Magnetometer", g_magLabel, "rotate slowly", "logging @200ms");
+  drawLines("Exercise 22", "Magnetometer", g_magLabel, "offsets applied", "logging @200ms");
   delay(kUiSplashMs);
   g_lastSampleMs = millis();
   g_lastDisplayMs = millis();