Configuration

The settings a BASIS-2 takes over Modbus, their ranges and defaults, and the order to apply them in.

Every setting here is a register write that the instrument keeps until you change it or restore the factory settings. Every snippet is compiled from tests/docs/configuration.cpp.

Order

Step	Call	Why this position
1	SetModbusAddress(), SetBaudRate()	Bus settings first, one instrument at a time (API guide)
2	ReadIdentity()	Flow units and full scale decide how to read every value
3	SetGas()	Calibration for the process gas
4	SetReferenceTemperatureC(), SetFlowAveragingMs(), SetTotalizerLimitMode()	How flow and total are reported
5	SetSetpointSource(), SetCommWatchdogMs(), SetAutotareEnabled(), SetMaxSetpointRamp()	Controllers: control behaviour
6	Tare()	Last, on the process gas with no flow

Meters and controllers

using al::DriverError;
DriverError e = meter.SetGas(al::Gas::Nitrogen).error;                     // register 2100
if (e == DriverError::None) e = meter.SetReferenceTemperatureC(20.0f).error;  // 52: 0..30 C
if (e == DriverError::None) e = meter.SetFlowAveragingMs(50).error;         // 55: 0..2500 ms
if (e == DriverError::None) {
  e = meter.SetTotalizerLimitMode(al::TotalizerLimitMode::ResetWithOvr).error;  // 54
}
return e == DriverError::None;

Setting	Call	Register	Range	Factory default
Gas	SetGas(Gas)	2100	Air, Argon, CarbonDioxide, Nitrogen, Oxygen, NitrousOxide, Hydrogen, Helium, Methane	Per order
Reference temperature	SetReferenceTemperatureC(float)	52	0 °C to 30 °C, in 0.01 °C	Not stated
Flow averaging	SetFlowAveragingMs(uint16_t)	55	0 ms to 2500 ms time constant	Not stated
Totalizer limit	SetTotalizerLimitMode(TotalizerLimitMode)	54	See below	Not stated
ASCII unit ID	SetAsciiUnitId(char)	46	'A' to 'Z'	'A'

The driver checks the ranges of the averaging time, the reference temperature, the address and the unit ID before it sends anything, and returns InvalidParameter or InvalidAddress. Writing a gas the instrument does not have leaves the gas unchanged (manual, register 2100).

TotalizerLimitMode	At the maximum total
SaturateNoError (0)	Hold the maximum, no OVR
ResetNoError (1)	Restart from zero, no OVR
SaturateWithOvr (2)	Hold the maximum, set OVR
ResetWithOvr (3)	Restart from zero, set OVR

Controllers only

using al::DriverError;
DriverError e = controller.SetSetpointSource(al::SetpointSource::DigitalUnsaved).error;  // 516
if (e == DriverError::None) e = controller.SetCommWatchdogMs(500).error;    // 514: 0..5000 ms
if (e == DriverError::None) e = controller.SetAutotareEnabled(true).error;  // 515
if (e == DriverError::None) {
  // 524-525: % of full scale per ms x 10^7. 0.01 %/ms (full scale in 10 s) = 100000.
  e = controller.SetMaxSetpointRamp(100000).error;
}
return e == DriverError::None;

Setting	Call	Register	Range
Setpoint source	SetSetpointSource(SetpointSource)	516	Analog (0), DigitalSaved (1), DigitalUnsaved (2)
Communication watchdog	SetCommWatchdogMs(uint16_t)	514	0 ms (off) to 5000 ms
Autotare	SetAutotareEnabled(bool)	515	Tares after the setpoint has been 0 for at least 2 s
Maximum setpoint ramp	SetMaxSetpointRamp(uint32_t)	524-525	% of full scale per ms × 107; 0 = no ramp
Batch volume	SetTotalizerBatch(uint32_t)	521-522	Total-volume units, scaled by the factory-set decimals

A meter has none of these registers and rejects the writes (API guide).

Driver settings

These live in the Driver object, not in the instrument.

Setting	Call	Default
Target address	constructor, SetAddress()	As constructed
Response timeout	constructor, SetTimeoutMs()	200 ms (kDefaultTimeoutMs)
Bus baud rate, for the inter-frame gap	SetBusBaudRate(); SetBaudRate() sets it too	38400 (kDefaultBusBaudBps)
Flow decimals	argument of ReadInstantaneous()	3

Back to factory settings

FactoryRestore() writes 0x5214 to register 80 and copies the factory settings over the user settings. The manual recommends a power cycle afterwards. It may change the address and the baud rate back, so expect to rediscover the instrument.