Hello,

I'm trying to understand the reface DX master tune parameter change sysex. As per the Yamaha Reface Data List, it consists of four bytes, described like this:

-102.4 – +102.3 (cent)
1st bit 3-0 : bit 15- 12
2nd bit 3-0 : bit 11- 8
3rd bit 3-0 : bit 7- 4
4th bit 3-0 : bit 3- 0

If understand this correctly, I should use the first 4 bits of the 4th byte as the first 4 bits of the final number, the first 4 bits of the 3rd byte as the next four bits of the final number, the first 4 bits of the 2nd byte as the next four bits of the final number and the first 4 bits of the 1st byte as the final 4 bits of the final number.

The final number / 10 - 102.4 should be the number of cents removed from 440.0 Hz.

The works if the master tune of the reface is set to 440.0. The value returned by the above calculation is 1024, so the master tune number is 102.4 -102.4, or zero, and the tuning is set to 440.0 Hz.

If the master tune setting of the reface is anything other than 440.0, the above calculation doesn't result in the same number of Hz as appears on the screen of the reface.

I think I must be unpacking the bit fields incorrectly.

Can anyone explain how they should be unpacked?

Thanks.

:Arn