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HardFOC driver

Alicat BASIS-2 Driver

A C++17 driver for Alicat BASIS-2 mass flow meters and controllers. It reads flow, temperature and the totalizer, commands setpoints, tares and reconfigures the instruments over Modbus-RTU, on any MCU with a UART and an RS-485 or RS-232 transceiver.

Quickstart API guide Source on GitHub

The driver has no platform code. You give it a small class that writes bytes, reads bytes with a timeout and flushes the receive buffer; it does the rest: Modbus-RTU framing, the CRC-16, reply checks, register scaling and error reporting. It is header-only and allocates nothing.

Thermal mass flow meter and controller BASIS-2 Alicat Scientific
Instruments
B-Series meters and BC-Series controllers, 100 SCCM to 20 SLPM full scale, 9 calibrated gases
Interface
RS-485 or RS-232 (by model), 8 data bits, no parity, 1 stop bit; 38400 baud default, 4800 to 115200
Protocols
Modbus-RTU (functions 03, 06, 16), which this driver uses; Alicat ASCII commands
Addressing
Modbus address 1 to 247; ASCII unit ID A to Z
Supply
12 V to 24 V DC; 210 mA (controller), 12 mA (meter)
Connector and limits
6-pin JST-GH; 145 PSIG maximum common-mode pressure

Operation manual (Rev 4, May 2025) ยท Alicat manuals

What you get

  • One object per instrument. Driver<YourUart> targets one Modbus address; several drivers share one port for a multidrop RS-485 bus. See API guide.
  • Live data in one request. ReadInstantaneous() reads registers 2100 to 2109 (gas, status, temperature, flow, total, setpoint, valve drive, batch) and decodes them. See API guide.
  • Control and configuration. Setpoint, setpoint source, watchdog, ramp, tare, totalizer, gas, averaging, reference temperature. See Configuration.
  • Bus bring-up. An address sweep, address and baud-rate changes, factory restore. See Modbus-RTU protocol.
  • Zero-overhead portability. The port is a CRTP class: no virtual calls, no heap, no exceptions, no RTOS dependency. See Porting.
  • Tested without hardware. Host unit tests run the driver against a model of a BASIS-2 Modbus slave. See Testing and CI.

Where to go next

  • Quickstart

    Wire the bus, write the port, read flow in about 15 lines.

  • Hardware

    Connector pinout, bus settings, timing and power.

  • Architecture

    The three layers and what each one owns.

  • API guide

    Read, command, configure and handle errors, task by task.

  • Porting

    Implement the serial interface for your MCU.

  • API reference

    Every class and member, generated from the headers.