FC IoT Command — Frequency Meters
The FC command configures frequency meters for IoT devices. It includes 2 meters (FC00-FC01) and 6 threshold triggers (FCT00-FCT05).
What is it for?
📊 Measure frequency — Counts pulses per second on OW ports
🚗 VSS Speed — Measures vehicle speed signal
⚙️ Engine RPM — Monitors revolutions per minute
🎯 Triggers — Generates events when frequency exceeds threshold
Description
Frequency meters use OW0 and OW1 ports to measure pulses per second. The value can be queried and scaled.
If an FC counter is enabled (factor > 0), it will occupy the OW port and will not allow temperature readings or OneWire devices.
⚡ IMPORTANT: The OW port is UNPROTECTED, @3.3VCC MAX. Do not exceed this voltage.
FC Syntax (Frequency Meter)
| Operation | Command | Description |
|---|---|---|
| Query | QFCaa | Reads frequency value |
| Configure | SFCaaSbb..bb,cc..cc | Defines factor and time base |
Response
RFCaa,ddddd,bbbbbbbb,cc| Field | Description |
|---|---|
aa | Counter index (00-01) |
ddddd | Frequency value (scaled) |
bb..bb | Scale factor (÷10000) |
cc..cc | Time base in seconds |
Calculation Formula
Value = (Pulses × (factor / 10000)) / timebaseFC Examples
Configure frequency meter
>SFC00S10000,1<
>RFC00,00000,00010000,01;ID=1234;*6B<
// Factor: 10000/10000=1, base: 1 secondWith pulses detected on OW0:
>QFC00<
>RFC00,00061,00010000,01;ID=1234;*6C<
// Measured frequency: 61 Hz ✅Configure with factor 9500
>SFC00S09500,01<
>RFC00,00000,00009500,01;ID=1234;*66<
// Factor: 9500/10000 = 0.95 (reduced scale)FCT Syntax (Threshold Triggers)
The FCT command generates events when frequency exceeds a configured threshold.
| Operation | Command | Description |
|---|---|---|
| Query | QFCTaa | Reads configuration |
| Configure | SFCTaabccccc | Defines trigger threshold |
Response
RFCTaabccccc| Field | Description |
|---|---|
aa | Trigger index (00-05) |
b | Port: 0=OW0, 1=OW1 |
ccccc | Frequency threshold |
The FCT signal will be 1 when frequency exceeds the threshold, and 0 when it’s lower. Generates FCT+ and FCT- edges for use in rules.
Associated Signals
| Signal | Index | Conditional Use | Edges |
|---|---|---|---|
| FCT | 00-05 | ✅ Yes | +/- both |
Compatibility
| Dispositivo | Notas |
|---|---|
Spider IoT | 1 FCT port |
Smart IoT | 2 FCT ports |