AC Command — Integrated Accelerometer
Real-time G-force value queries.
What is it used for?
| Use case | Description |
|---|---|
| 📊 Driving monitoring | Detect accelerations, braking and sharp turns |
| 🚗 Movement detection | Identify when the vehicle is in motion |
| ⚠️ Impact alerts | Trigger alerts when G thresholds are exceeded |
| 📐 Inclination | Verify device position and orientation |
Description
Allows querying G-force (acceleration) values measured by the integrated accelerometer in the hardware. Resulting or absolute magnitudes of up to 8G can be measured in three axes (X, Y, Z).
Features
- 3-axis measurement (X, Y, Z)
- Range: 8G
- Resolution: Hundredths of G
- Configurable triggers via CXAC
The AC trigger is NOT recommended for conditional use in event engine rules. Use AC+ edges only in triggers (TRG).
Commands
Query accelerometer
QACResponse:
RAC Xsaaa Ysbbb Zsccc Rsrrr.r Psppp.p Ee RAW Xsxxx Ysyyy ZszzzParameters:
- s: Sign (+ or -), positive reference = gravity acceleration
- aaa, bbb, ccc: X, Y, Z axes calibrated, in hundredths of G
- rrr.r: Real-time roll angle, in degrees with one decimal
- ppp.p: Real-time pitch angle, in degrees with one decimal
- e: Calibration enabled (1) or not (0)
- xxx, yyy, zzz: The same three axes uncalibrated, in hundredths of G
The response carries ten fields, not three. Besides the calibrated axes it includes the roll and
pitch angles, the calibration status and the three raw axes. A parser that cuts off after Z will
discard half the information.
Examples
Query at rest
>QAC<
>RAC X+000 Y+018 Z+100 R+000.5 P-001.2 E1 RAW X+002 Y+020 Z+102;ID=1234;+18<Interpretation:
- Z+100: 1.00G (gravity acceleration, vehicle at horizontal rest)
- Y+018: 0.18G (small lateral inclination)
- X+000: 0.00G (no longitudinal acceleration)
Rule with acceleration trigger
>SRL10E;TRG=AC+;ACC={GGPXXL}<Generates GP report each time the acceleration threshold configured via CXAC is exceeded.
Threshold Configuration
Acceleration thresholds are configured via the CXAC Command.
The AC trigger remains active for 1 second after exceeding the configured threshold.
AC Signals
Available edges
| Signal | Activation |
|---|---|
AC+ | Exceeded acceleration threshold (configured in CXAC) |
Restrictions
- Only positive edge (+) available
- NOT suitable for use in conditionals (CND)
- Only use in triggers (TRG)
- Duration: 1 effective second
Value Interpretation
Axis reference
According to standard installation orientation:
- X-axis: Longitudinal (vehicle forward/backward)
- Y-axis: Lateral (left/right)
- Z-axis: Vertical (up/down)
Typical values
| Situation | X | Y | Z |
|---|---|---|---|
| Horizontal rest | 0.05G | 0.05G | +1.00G |
| 0.5G acceleration | +0.50G | 0.05G | +1.00G |
| 0.5G braking | -0.50G | 0.05G | +1.00G |
| Right turn | 0.05G | -0.30G | +1.00G |
| Left turn | 0.05G | +0.30G | +1.00G |
Response Breakdown
QAC Example
>QAC<
>RAC X+000 Y+018 Z+100 R+000.5 P-001.2 E1 RAW X+002 Y+020 Z+102;ID=1234;+18<| Field | Value | Interpretation |
|---|---|---|
RAC | - | Accelerometer Response |
X+000 | +0.00G | X-axis calibrated: no acceleration |
Y+018 | +0.18G | Y-axis calibrated |
Z+100 | +1.00G | Z-axis calibrated: normal gravity |
R+000.5 | +0.5° | Real-time roll |
P-001.2 | −1.2° | Real-time pitch |
E1 | 1 | Calibration enabled |
RAW X+002 | +0.02G | Uncalibrated X-axis |
RAW Y+020 | +0.20G | Uncalibrated Y-axis |
RAW Z+102 | +1.02G | Uncalibrated Z-axis |
ID=1234 | 1234 | Identifier |
+18 | 18 | Checksum |
Limitations
- Don’t use AC in CND: Only in triggers (TRG)
- Short duration: Signal active for 1 second
- Calibration: Requires correct device installation
- Sensitivity: Configure thresholds according to application
Compatibility
See Also
- CXAC Command - Threshold configuration
- SS Command - Signal queries
- Event Engine - Use in rules
- Trigger List - AC signal