MIDI serial BAUD rate

Hi I’m trying to set a MIDI connection through serial port 4

echo something > /dev/ttyO4
works if I select one of the baud rates defined in termios.h (say 38400) but doesn’t work for 31250 (the MIDI baud rate).

I have flashed to 4.1 (uname -r == 4.1.2-ti-r4) and can get a 500k Baud serial port from another UART. With the idea that setting a divisor would work out to the desired BAUD if I could set a divisor of 16. I have another UART that needs to run at 1 MBaud.

Is there someway of putting in a custom baud divisor in c code ideally?

This is where I am at:

void initializeBBB() {

FILE *uartFileManager;
//UART config using termios
struct termios midiTermios, picTermios, tempTermios;

midiDevice = open( “/dev/ttyO4”, O_RDWR | O_NOCTTY );
if ( midiDevice < 0 ) {
printf(“Error: MIDI connection failed to open”);

tcgetattr( midiDevice, &tempTermios );
bzero( &midiTermios, sizeof( midiTermios ) );
midiTermios.c_cflag = B500000 | CS8 | CLOCAL | CREAD;
midiTermios.c_iflag = IGNPAR | ICRNL;
midiTermios.c_oflag = 0;
midiTermios.c_lflag = 0;

midiTermios.c_cc[VTIME] = 0;
midiTermios.c_cc[VMIN] = 1;

tcflush( midiDevice, TCIFLUSH );
tcsetattr( midiDevice, TCSANOW, &midiTermios );


which will initialize ttyO4 to 500000 Baud. Placing in:

cfsetispeed(&midiTermios, 31250);
cfsetospeed(&midiTermios, 31250);

before tcsetattr did not accomplish setting.

midiTermios.c_ispeed = 31250;
midiTermios.c_ospeed = 31250;

also didn’t work. Are there ioctl commands available on the BBB? Any help that doesn’t make me use a MIDI → USB cable and connect that way would be appreciated. I would really like to not have to recompile the kernel.



Is there someway of putting in a custom baud divisor in c code ideally?

Yes. Peter Hurdley just posted a link to some code to do exactly that on the forums here. The subject title was Portuguese( I think ), so should stand out if you search Peter’s name, and sort by date.

Sorry, I say “just”, but Peter posted that link like a week or slightly longer. Ago.


That’s it, second post form the bottom. Make sure to thank Peter for sharing his code.