LCD MIDI + MIDI Serial baud rate info
Just pondering a few numbers with regards to my last post about USB-MIDI and baud rates, I realise this may be basic stuff to some but thought I would post it here just incase it was beneficial to anyone. I have done a few calculations related to the amount of bandwidth the LCD MIDI setup might take from a serial MIDI data stream, here are my findings….
1 MIDI CC message = x3 bytes (status, data, data) = 24 bits per message.
The LCD characters need two MIDI CC messages so a total of 48 bits to be sent to display a character.
There are 12 characters displayed by the HC4500 so 12 * 48 = 576 bits needed to display the whole line.
Both track and artist are on a separate line so 576 * 2 = 1152 bits are needed to display two lines with track and artist.
The update of minutes within the track time requires one message = 24 bits
The update of seconds within the track time requires one message = 24 bits
The update of frames within the track time requires one message = 24 bits
so…. If during 1 second of time, everything on the display needs to be updated…
(im not sure how many times track and artist scroll along the line in a second, lets say six times for an extreme example)
1152 * 6 = 6912 bits to move track and artist within the given second
24 bits to change minutes
24 bits to change seconds
100 * 24 bits to change frames (as 100 frames count over in 1 second)
= 9360 bits are required maximum to update all information over the period of one second
9360 x 2 = 18,720 bits for both decks
18,720 / 31250 * 100 = 59.9% of the MIDI bandwidth taken up.
So to conclude, even with the maximum amount of messages being transmitted at any given time for both decks transmitting data for the LCD MIDI display, there is still almost half of the MIDI in bandwidth remaining, meaning 31,250bps standard serial MIDI should have no problem coping with the amount of data. I don't think the display actually scrolls 6 times a second (if it scrolls twice in a second the bandwidth drops to 30%) and is Traktor really going to need 40% of the bandwidth to Transmit all other MIDI message which will probably consist of a few messages to switch a few LEDs on and off periodically! :)