Hi
Thanks for all the information and for the quick response. I have found the Midi Implementation Document for the VM-C7200. It apears that the faders resolution is 128 steps only, but the message includes a checksum after the data bytes and before the End of Exclusive flag. The message format is as follows:
Data Set (Dt1)
Status Data byte Status
F0H 41H, Dev, 00H, IEH, 12H, aaH, bbH, ccH, ddH, ..., eeH, Sum F7H
Byte Description
F0H Status of System Exclusive Message
41H Manufacturer ID (Roland)
Dev Device ID
00H 1EH Model ID (V-Mixer)
12H Command ID (Dt1)
aaH Address MSB
bbH Address MID
ccH Address LSB
ddH Data
: :
eeH Data
Sum Checksum
F7H End of Exclusive
There is a Parameter Address Block that list the starting address for the main blocks. There are sub-blocks that contain the offset address for each parameter from the starting address of the main block.
For the channel 1 level fader it goes something like this:
Block: Start Address: Offset Address: Data:
VM-7x00 Unit 1 Mixer Block 00 10 00
Input parameters -1 (ch1) 00 00 30
Input parameters -2 (ch2) 00 01 20
: :
Input parameters -24 (ch24) 00 14 40
Input Mute Switch 00 00 23 00 - 01
Input Master Fader Level 00 00 24 00 - 7F
Input Main Send Pan 00 00 26 00 - 7F
On Roland system exclusive message (Dt1), a checksum is added at the end of transmitted data (in front of F7H) to check the message is received correctly. Value of checksum is defined by addres and data (or size) of the system exclusive message to be transmitted.
How to calculate checksum (Hexadecimal number is shown with H.)
Checksum is a value which lower 7 bit of the sum of address, size and checksum itself turns to be 0. For example, if the address of the system exclusive message to be transmitted is aa bb ccH and data or size is dd ee ffH:
aa + bb + cc + dd + ee +ff = sum
sum / 128 = quotient and odd
When odd is 0, 0 = Checksum
When odd is other than 0, 128 - odd = Checksum
I don´t have Access to the mixer at this time, but let me check tomorrow for some real messages transmited to verify. I think that the checksum will be important in order to have propper feedback. Thanks!!!