Industrial Fieldbus EIA/TIA-232-E / EIA-485 / UART
OpenRFID Driver: OpenRFID.Plugins.Serial RS-232 & RS-485 Serial UART Communication
RS-232 and RS-485 define point-to-point and multi-drop differential electrical signaling. Used extensively for microcontrollers (ESP32, STM32), point-of-sale RFID desktop pads, and long-distance factory floor reader clusters.
Layer / Stack
Physical & Data Link (Serial COM)
Default Port / Freq
COM Port (9600, 19200, 38400, 57600, 115200 Baud)
Throughput / Speed
Up to 1.2 km cable distance (RS-485) | Up to 15 m (RS-232)
Standard Body
EIA
Core Protocol Architecture & Specifications
- ✓ Differential signaling on RS-485 (A/B lines) providing high noise immunity against factory VFD motors
- ✓ Multi-drop bus topology supporting up to 32 reader nodes on a single 2-wire twisted pair up to 1,200 meters
- ✓ Standard framed packet structures with 0xAA / 0x55 synchronization headers and CRC-16 error checksums
- ✓ Configurable baud rates (9600 to 115200 bps), 8 data bits, 1 stop bit, no parity (8-N-1)
- ✓ Direct compatibility with POS cash registers, weighbridges, and CNC controllers
OpenRFID .NET 8 Serial Hex Frame Parser with CRC-16 Check
csharp using System.IO.Ports;
public class SerialRfidParser
{
// Standard Hardware Frame: [0xAA, Len, ReaderAddr, CmdCode, Data..., CRC16_Hi, CRC16_Lo]
public const byte FRAME_HEADER = 0xAA;
public static bool TryParseFrame(ReadOnlySpan<byte> buffer, out byte[] epcBytes)
{
epcBytes = Array.Empty<byte>();
if (buffer.Length < 7 || buffer[0] != FRAME_HEADER) return false;
byte len = buffer[1];
if (buffer.Length < len + 2) return false;
// Verify CRC-16 CCITT
ushort calculatedCrc = ComputeCrc16(buffer.Slice(1, len - 1));
ushort receivedCrc = (ushort)((buffer[len] << 8) | buffer[len + 1]);
if (calculatedCrc != receivedCrc) return false;
byte cmd = buffer[3];
if (cmd == 0x01) // Inventory Read Command
{
byte epcLength = buffer[4];
epcBytes = buffer.Slice(5, epcLength).ToArray();
return true;
}
return false;
}
private static ushort ComputeCrc16(ReadOnlySpan<byte> data)
{
ushort crc = 0xFFFF;
foreach (byte b in data)
{
crc ^= (ushort)(b << 8);
for (int i = 0; i < 8; i++)
crc = (crc & 0x8000) != 0 ? (ushort)((crc << 1) ^ 0x1021) : (ushort)(crc << 1);
}
return crc;
}
}Verified Hardware Implementations
Our engineering team has thoroughly tested and validated RS232 / RS485 Serial across the following reader models, embedded modules, and smart transponders:
Chainway C72 Internal UART Bus Desktop UHF RFID USB/Serial Pads Industrial Boom Barrier Readers Identium Serial Fixed Portals
Target Deployments
- Toll plaza boom barrier vehicle readers
- Jewelry desktop tray stock audit pads
- Weighbridge truck identification
- Embedded handheld terminals
Deploy with OpenRFID
Integrate RS232 / RS485 Serial into your ERP, warehouse software, or custom mobile app with pre-built C# / C++ drivers.
What is the maximum distance for RS-485 vs RS-232 RFID readers?
RS-232 is limited to 15 meters (50 feet) due to single-ended signaling. RS-485 uses balanced differential pairs and can reliably transmit tag data up to 1,200 meters (4,000 feet) in noisy industrial plants.