Promag MF7S RFID Reader

Description

The Promag MF7S is an RFID card reader that communicates via RS-232 (19200 baud, 8N1). The reader automatically transmits the card UID when a card is presented. CHESTER runs a background listener thread that continuously receives cards and stores them in a buffer (max 32 samples).

Protocol: STX(0x02) + 8 HEX characters (UID) + CR + LF + ETX = 12 bytes per card.

Hardware

Variant: CHESTER Serial RS-232 (hio-chester-serial-rs232)
Module: CHESTER-X12-A (RS-232)
Connection: Promag MF7S → RS-232 → CHESTER-X12-A
Baud rate: 19200 (fixed, set by driver)

Configuration

Shell Commands

app config serial-mode transparent
app config serial-baudrate 19200
app config serial-data-bits 8
app config serial-parity none
app config serial-stop-bits 1
app config device-0 promag_mf7s
app config mode lte
app config interval-report 0
app config save

Parameter Reference

Parameter	Value	Description
`serial-mode`	`transparent`	Promag does not use Modbus
`serial-baudrate`	`19200`	Fixed for MF7S
`device-0`	`promag_mf7s`	Device type (no address — not Modbus)
`mode`	`lte` or `lrw`	Communication mode
`interval-report`	`0`	Event-driven = immediate send on card detection

Event-Driven Mode (`interval-report = 0`)

When interval-report is set to 0, CHESTER sends data immediately after a card is presented:

LTE mode: Each card triggers app_work_send() → CBOR message with the card is sent immediately
LoRaWAN mode: Each card is always sent immediately (independent of interval-report)

When interval-report > 0, cards accumulate in the buffer (max 32) and are sent periodically.

Shell Commands — Driver

Read Reader Firmware Version

device promag_mf7s firmware

Output: Firmware: MF7S-1.0

Notifications (LED + Sound)

device promag_mf7s notify

Performs the sequence: green LED on/off → red LED on/off → triple beep (high, medium, low).

Sampling Mode (Interactive Detection)

device promag_mf7s sampling [timeout_s]

Enters interactive mode — displays card UIDs in the shell. Data is not stored in the buffer. The timeout (default 10 s) resets on each card presentation.

Output:

Sampling mode active (idle timeout: 10s)
Present cards to the reader...
Card UID: 12345678 (dec: 305419896)
Card UID: AABBCCDD (dec: 2864434397)
Sampling finished (total reads: 2)

Other Commands

device sample 0        # Show device status at index 0
device list            # List configured devices
app send               # Force immediate data send

Payload — LTE (CBOR)

LTE mode sends a CBOR message (max 8 KB) with all collected cards. The buffer is cleared after a successful send.

Example Decoded JSON Payload

{
  "message": {
    "version": 2,
    "sequence": 1,
    "timestamp": 1735905238
  },
  "attribute": {
    "vendor_name": "HARDWARIO",
    "product_name": "CHESTER-M",
    "hw_variant": "CDGLS",
    "hw_revision": "R3.4",
    "fw_version": "v3.5.1",
    "serial_number": "2159019335"
  },
  "system": {
    "uptime": 3600,
    "voltage_rest": 3.65,
    "voltage_load": 3.42,
    "current_load": 38
  },
  "network": {
    "parameter": {
      "eest": 7,
      "ecl": 0,
      "rsrp": -85,
      "rsrq": -8,
      "snr": 12,
      "plmn": 23003,
      "cid": 12345678,
      "band": 20,
      "earfcn": 6300
    }
  },
  "thermometer": {
    "temperature": 23.45
  },
  "accelerometer": {
    "accel_x": 0.01,
    "accel_y": -0.02,
    "accel_z": 1.00,
    "orientation": 2
  },
  "devices": [
    {
      "device": 0,
      "type": 11,
      "type_name": "promag_mf7s",
      "addr": 0,
      "data": [
        {
          "timestamp": 1735905200,
          "card_uid": 305419896
        },
        {
          "timestamp": 1735905230,
          "card_uid": 2864434397
        }
      ]
    }
  ]
}

info

card_uid is a uint32 (decimal). Hex conversion: 305419896 = 0x12345678, 2864434397 = 0xAABBCCDD.

Payload — LoRaWAN (Binary)

LoRaWAN sends a compact binary message (max 51 bytes). Each message contains one device.

Payload Structure (22 bytes)

Offset  Size  Field
------  ----  -----
     1B    Header: [version:4bit=1][device_idx:4bit]
     5B    Battery (CHESTER standard encoding)
     1B    Accelerometer orientation
     2B    Thermometer (INT16 LE, /100 °C)
     1B    Device type (11 = PROMAG_MF7S)
    1B    Device address (0)
    1B    Status flags (0x01=valid)
    4B    Card UID (big-endian)
    4B    Timestamp of last read (little-endian, unix)
    2B    Total reads counter (uint16 LE)

Total size: 22 bytes

Example Payload (hex)

                   # Header: version=1, device_idx=0
0E 0F D2 0D 26         # Battery: rest=3650mV, load=3421mV, current=38mA
                   # Accelerometer: orientation=2
09                  # Thermometer: 2345 → 23.45°C
0B                     # Device type: 11 (promag_mf7s)
                   # Address: 0
                   # Status: valid
34 56 78            # Card UID: 0x12345678 (BE)
D0 E0 4B 67            # Last read timestamp: 1735905488 (LE)
00                  # Total reads: 2

Decoding in Node-RED / JavaScript

function decode(payload) {
    var buf = Buffer.from(payload, 'hex');
    var offset = 0;

    var header = buf.readUInt8(offset++);
    var version = (header >> 4) & 0x0F;
    var device_idx = header & 0x0F;

    // Skip system data (8 bytes)
    offset += 8;

    var device_type = buf.readUInt8(offset++);
    var device_addr = buf.readUInt8(offset++);
    var status = buf.readUInt8(offset++);

    // Promag MF7S (type 11)
    if (device_type === 11) {
        var uid = buf.readUInt32BE(offset); offset += 4;
        var timestamp = buf.readUInt32LE(offset); offset += 4;
        var total_reads = buf.readUInt16LE(offset); offset += 2;

        return {
            device_idx: device_idx,
            device_type: "promag_mf7s",
            card_uid: uid.toString(16).toUpperCase().padStart(8, '0'),
            card_uid_dec: uid,
            last_read_timestamp: timestamp,
            total_reads: total_reads,
            valid: (status & 0x01) !== 0
        };
    }
}

Typical Use Cases

Access Control / Attendance System (Immediate Send)

app config device-0 promag_mf7s
app config mode lte
app config interval-report 0
app config save

Each card is sent immediately after being presented.

Data Collection with Periodic Upload (Battery Saving)

app config device-0 promag_mf7s
app config mode lte
app config interval-report 900
app config save

Cards accumulate in the buffer (max 32) and are sent every 15 minutes.

LoRaWAN Mode

app config device-0 promag_mf7s
app config mode lrw
app config save

Each card is sent immediately as a binary message (22 bytes). Always sends the last presented card plus a total read counter.

Description​

Hardware​

Configuration​

Shell Commands​

Parameter Reference​

Event-Driven Mode (interval-report = 0)​

Shell Commands — Driver​

Read Reader Firmware Version​

Notifications (LED + Sound)​

Sampling Mode (Interactive Detection)​

Other Commands​

Payload — LTE (CBOR)​

Example Decoded JSON Payload​

Payload — LoRaWAN (Binary)​

Payload Structure (22 bytes)​

Example Payload (hex)​

Decoding in Node-RED / JavaScript​

Typical Use Cases​

Access Control / Attendance System (Immediate Send)​

Data Collection with Periodic Upload (Battery Saving)​

LoRaWAN Mode​