SignalConverter

SignalConverter converts a quantity in both directions at once. One port multiplies by a gain and adds an offset; the other subtracts the offset and divides. The two are exact inverses, so a value sent out and read back comes home unchanged.

Use it wherever a quantity crosses a unit boundary both ways — a setpoint going out to hardware and a measurement coming back.

flowchart LR
    i1(["input"]) --> B["SignalConverter"]
    i2(["inverseInput"]) --> B
    p1(["gain"]) --> B
    p2(["offset"]) --> B
    p3(["inverseOutputReference"]) --> B
    p4(["doReferencing"]) --> B
    p5(["doReferencingAll"]) --> B
    p6(["invert"]) --> B
    B --> o1(["output"])
    B --> o2(["inverseOutput"])

invert decides which port multiplies. With it false — the default — inverseOutput multiplies and output divides. With it true they swap. Everything else about the block is the same.

Automatic referencing does not work correctly at the default invert setting. It computes an offset that suits the other direction, so unless your gain is 1 the result will be wrong. Set the offset by hand, or set invert to true, until this is fixed.

Signals

Inputs

Outputs

Parameters

All are persistent and survive a controller restart. doReferencing and doReferencingAll are persistent too, so a configuration saved while one was set will re-reference on the next startup, against whatever the inputs happen to read then. Save your configuration after referencing, not during.

No parameters exist below this block.

Setup

1. Connect the two directions. With invert false, the multiplying direction is inverseInput to inverseOutput.
2. Set gain per channel, from the units: it is the multiplying side’s output unit divided by its input unit.
3. Leave offset at 0 for now.
4. Feed a known value into inverseInput and confirm inverseOutput is that value times the gain.
5. Feed inverseOutput back into input and confirm output returns the original. The round trip should be exact.
6. Set the offset by hand from a known reference point — see the caveat about automatic referencing above.

Tuning

1. There is nothing dynamic here. Both parameters take effect on the next cycle, with no fade and no filtering.
2. Set the gain from the units first, and check the round trip before worrying about the offset.
3. Set the offset from one known point: put the machine at a position you can measure, read inverseInput, and compute the offset that makes inverseOutput read the true value.
4. If you use doReferencing, verify the result rather than trusting it — read offset back and check inverseOutput really lands on inverseOutputReference. At a gain of 1 it will; away from 1 it will not.
5. Check both directions after every change. The two share one gain and one offset, so a change intended for one affects the other.
6. Use a gain of 0 deliberately if you want a channel’s dividing side muted — it outputs 0 rather than failing.
7. Nothing here depends on the task rate.

The dashed line is the round trip. It should always be the identity.

A starting point for a two-channel pass-through:

gain    = [1.0, 1.0]
offset  = [0.0, 0.0]
invert  = false

Limits and errors

This block logs nothing, ever. Every condition above shows as a value on a trace, or not at all.

Verified against motorcortex-control3 3.30.0 (bc348fd).