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Midi PC max 127- why?

54321pj

Inspired
Hi guys, just wondering why is there a maximum Midi PC of 127?
I’m using a boss Es-8 to send the program changes, and use it to change through presets and scenes. When mapped out on the III, I can only get 16 presets with 8 scenes in each.. Then the axe runs out out of PC numbers. The boss Es-8 has 99 presets with 8 scenes in each, so I’m assuming that’s a lot of PC changes available, like 792! It has way more, which I cant utilize.
Is there a reason for this? Is this something that could be expanded upon with future firmware updates?
 

simonp54

Experienced
MIDI is a standards based 7 bit data protocol. That yields options for data elements up to 127 (128 options) in any single field. This is why MIDI banks exist. Effectively Preset 129 is Bank 2 PC 1. This is further "complicated" for new users because the numbering starts at 0 as the first preset/bank. so bank 2 is sent as 1 and preset numbers then run within that bank from 0 - 127. The AXEFXIII has 4 banks (0, 1, 2, 3) for its 512 presets (0-511) to select preset 512 set bank 3 and PC 127
 

Capt Nasty

Experienced
This is why FAS is using MIDI Sys Ex messages for communication between the Axe FX and FC. Sys Ex messages allow developers to define their own message format. This side steps the limitations imposed by the MIDI specification
 

simonp54

Experienced
@Capt Nasty - it doesn't side step the limitations of 7 bit data. but yes, formats which take into account larger data ranges are able to be handled differently.
 

Capt Nasty

Experienced
@Capt Nasty - it doesn't side step the limitations of 7 bit data. but yes, formats which take into account larger data ranges are able to be handled differently.
If you can define you own message format then yes it absolutely does sidestep the limitation.

MIDI PC, CC are fixed format messages which happen to have a fixed length on the fields within the message data payload.

MIDI Sys Ex does NOT have a fixed length on the data payload therefore the programmer can send much larger, properietary message payloads via Sys Ex.

So yes, it absolutely does side step the limitations of MIDI PC/CC messages.
 

simonp54

Experienced
If you can define you own message format then yes it absolutely does sidestep the limitation.

MIDI PC, CC are fixed format messages which happen to have a fixed length on the fields within the message data payload.

MIDI Sys Ex does NOT have a fixed length on the data payload therefore the programmer can send much larger, properietary message payloads via Sys Ex.

So yes, it absolutely does side step the limitations of MIDI PC/CC messages.
well, yeah, but each byte can only be up to 7 bits.
 

Capt Nasty

Experienced
Well yeah, but you have unlimited byte fields with sys ex... just like a string. You serialize a custom data structure to binary then store it in the data field of the Sys Ex message where it functions as an array of bytes.

I would also point out since we are being pedantic, a word in a MIDI message is 8 bits not 7. The most significant bit in each word is the sign bit and is always set to “0”, thus indicating that MIDI does not allow negative values in a MIDI word.
 
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54321pj

Inspired
Thanks for the replies so far - although if I have understood one thing here, it’s just how little I know about midi :oops:
Am I right in thinking then, that after my boss sends its 128 pc command (which is 17 presets utilizing all 8 scenes in each) that the axe III can no longer use any more commands to enable say preset 18?
The Boss es-8 does have the ability to send midi on different channels, I’m currently sending on channel 1. Does the axe have the ability to ‘listen’ for pc commands on channel 2 for example? I can’t see this availability in the midi menu or midi mapping menu.
My thinking being, once 0-127 has been used on channel 1, for presets 1 thru 17, I could then get the boss to change to channel 2 for presets 18 thru 34. Using another 128 pc commands???
Is this possible?
 

unix-guy

Legend!
Thanks for the replies so far - although if I have understood one thing here, it’s just how little I know about midi :oops:
Am I right in thinking then, that after my boss sends its 128 pc command (which is 17 presets utilizing all 8 scenes in each) that the axe III can no longer use any more commands to enable say preset 18?
The Boss es-8 does have the ability to send midi on different channels, I’m currently sending on channel 1. Does the axe have the ability to ‘listen’ for pc commands on channel 2 for example? I can’t see this availability in the midi menu or midi mapping menu.
My thinking being, once 0-127 has been used on channel 1, for presets 1 thru 17, I could then get the boss to change to channel 2 for presets 18 thru 34. Using another 128 pc commands???
Is this possible?
You only want the Axe Fx listening on one channel... So using different channels is not a solution.

The real issue you are dealing with is that you are using midi mapping to get to Scenes.

This is not optimal for the exact reason you have discovered.

I assume the ES-8 doesn't allow sending CC data values, only 0 and 127?
 

Capt Nasty

Experienced
After looking at the ES-8 manual, each patch on the ES-8 can transmit a MIDI PC (Program Change) and/or a MIDI CC (Control Change).

With this being the case, if the Axe FX supports it I would use MIDI PCs to change Presets and MIDI CCs to change Scenes.
 

unix-guy

Legend!
Yeah... Both pages 10 and 19 refer to sending CC numbers and values.

So, yeah, much better choice than preset mapping.
 
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