Situation: You want to send the same format of System Exclusive messages that the Roland FC-300 foot controller sends so that you can control the Roland FR-4x accordion. You have already determined the System Exclusive messages that the foot switches send. Now you are trying to determine the System Exclusive messages the expression pedals send.
Note: There are two expression pedals on the Roland FC-300. Each expression pedal has a dual function:
- You can tilt the pedal between heel down and toe down to control the value of some effect.
- If you press firmly on the toe end of the pedal, you can toggle an effect off or on.
The FC-300 manual describes the System Exclusive messages that it sends starting on page 64. Based on the manual and your notes, the System Exclusive messages use the following pattern:
F0 41 10 00 00 20 12 w x y z F7
w Address Big
x Address Small
y Data
z Checksum
Here are the messages for the expression pedals:
F0 41 10 00 00 20 12 w x y z F7
Expression Pedal 1 tilt min F0 41 10 00 00 20 12 24 00 00 5C F7
Expression Pedal 1 tilt max F0 41 10 00 00 20 12 24 00 7F 5D F7
Expression Pedal 2 tilt min F0 41 10 00 00 20 12 24 01 00 5B F7
Expression Pedal 2 tilt max F0 41 10 00 00 20 12 24 01 7F 5C F7
Expression Pedal 1 toggle off F0 41 10 00 00 20 12 22 00 00 5E F7
Expression Pedal 1 toggle on F0 41 10 00 00 20 12 22 00 7F 5F F7
Expression Pedal 2 toggle off F0 41 10 00 00 20 12 22 01 00 5D F7
Expression Pedal 2 toggle on F0 41 10 00 00 20 12 22 01 7F 5E F7
In the tilt messages, the data value (y) can be between hex 00 and 7F (decimal 0 and 127).
To generate the correct checksum (z), follow these steps:
A. In decimal, find the sum of w + x + y.
B. Find the reminder of A divided by 128.
C. Calculate 128 - B.
Use the result from step C in hex as the checksum.