Many of our products are controlled and programmed via MIDI System Exclusive Messages. Unfortunately, creating of that messages is very difficult for most musicians because these messages use a “Checksum” byte in their structure. Calculating of the “Checksum” byte requires at least basic knowledge of work with binary or hexadecimal numbers. But it is no problem to create the checksum with help of our special CHD Checksum Calculator.
The calculator need no installation. It is based on Java script so it can be launched under any operational system which disposes with a web browser. Download and unpack archive containing the calculator and then launch it in a web browser – the CHD Checksum Calculator window opens.
If you don’t want to download and to run the script, also on-line version of the calculator is available (see below).
|CHD Checksum Calculator|
 to [F] buttons are used for enter of partial hex characters of calculated bytes (note that only bytes with value from 0h to 7Fh are accepted!)
[Clr] (Clear) button clears all
[CE] (Clear Entry) button clears only last inserted byte
[+] (Add) button is used for adding of next byte to checksum
[=] (Checksum Result) button calculates complete checksum and shows it on calculator’s display
Calculate checksum for the [F0h 00h 20h 21h 7Fh 55h 01h 24h xx F7h] SysEx message, where “xx” is the checksum byte. Byte stream for checksum calculating starts at the “55h” byte.
It is necessary to calculate the 7-bit complement of the sum of bytes 55h 01h 24h (by other words, seven-bit sum of bytes 55h, 01h, 24h and xx must be equal to zero).
Pres sequentially the   [+]  [+]   [=] buttons. Calculator shows “ChSum = 06 [hex]” on its display. So “06” is required hexadecimal value necessary for the “xx” checksum byte in the SysEx message.
|CHD Checksum Calculator (SW)||ZIP archive with Java script based software|
|Checksum Calculator Usage||PDF document|