Hacking the Jamman – It works (almost)…

I received the latest firmware upgrade (1.79) for the Beat Buddy today so I installed it  and gave my rig a try. It worked perfectly, right until it didn’t!

So here’s what I am playing with. I have two MIDI interfaces for the Arduino. One is a MIDI shield that uses the on board UART  and one is a DIY thing I put together using a breakout board. For the shield interface I am using the Arduino MIDI library and for the DIY setup I am using the SoftwareSerial library. The difference is that with the SoftwareSerial library I can use different pins on the Arduino as the input and output pins which lets me see diagnostic messages I put in the code (to see what the heck is going on!) using the Serial Monitor part of the Arduino toolkit.

So first off I tried it using the MIDI shield and it worked fine right until I tried to set 130 BPM as the tempo. Then it just did not work.

So I switched to the DIY board so that I could see the values I was sending in the code. That interface worked fine all all tempos.

So next up I hooked up the MIDI shield to my iPad using an iRig MIDI interface and used a little app to ‘see’ the midi that was actually being sent.

What I found was that it was fine until I tried to go above 127 BPM, then the data that the code was sending was just plain wrong! Now the same calculation works fine in my DIY code so it has to be something in the Arduino midi library that is messing things up but aso far I’ve no idea what.

I also noticed that even though the CC message I am sending is only supposed to have three bytes in it, the library seems to be sending an extra data byte which further leads me to believe that there’s something wrong in the library.

That’s a shame because using the library makes my code very simple which means it is also much easier to modify in the future. However it’s of no use if it does not work so I may well have to stick with my roll your own code for now because at least that works!


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