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diff --git a/backends/mqtt.md b/backends/mqtt.md index 895831c..6623438 100644 --- a/backends/mqtt.md +++ b/backends/mqtt.md @@ -30,10 +30,42 @@ The MQTT protocol places very few restrictions on the exchanged data. Thus, it i and output data formats accepted respectively output by the MIDIMonster. The basic format, without further channel-specific configuration, is an ASCII/UTF-8 string representing a floating -point number between `0.0` and `1.0`. The MIDIMonster will read these and use the value as the normalised event value. +point number between `0.0` and `1.0`. The MIDIMonster will read these and use the value as the normalized event value. -Values above the maximum or below the minimum will be clamped. The MIDIMonster will not output values out of those -bounds. +Channels may be specified to use a different value range or even freeform discrete values by preconfiguring +the channels in the instance configuration section. This is done by specifying options of the form + +``` +<channel> = range <min> <max> +<channel> = discrete [!]<min> [!]<max> <value> +``` + +Example configurations: +``` +/a/topic = range -10 10 +/another/topic = discrete !0.0 0.5 off +/another/topic = discrete 0.5 !1.0 on +``` + +Note that there may be only one range configuration per topic, but there may be multiple discrete configurations. + +The first channel preconfiguration example will change the channel value scale to values between `-10` and `10`. +For input channels, this sets the normalization range. The MIDIMonster will normalize the input value according to the scale. +For output channels, this sets the output scaling factors. + +The second and third channel preconfigurations define two discrete values (`on` and `off`) with accompanying normalized +values. For input channels, the normalized channel value for a discrete input will be the value marked with an exclamation mark `!`. +For output channels, the output will be the first discrete value for which the range between `<min>` and `<max>` contains +the normalized channel value. + +These examples mean +* For `/a/topic`, when mapped as input, the input value `5.0` will generate a normalized event value of `0.75`. +* For `/a/topic`, when mapped as output, a normalized event value `0.25` will generate an output of `-5.0`. +* For `/another/topic`, when mapped as an input, the input value `off` will generate a normalized event value of `0.0`. +* For `/another/topic`, when mapped as an output, a normalized event value of `0.75` will generate an output of `on`. + +Values above the maximum or below the minimum will be clamped. The MIDIMonster will not output values out of the +configured bounds. #### Channel specification |