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FunkyLabRat
Joined: 13 Feb 2012
Posts: 10
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| Transmitting MIDI messages with PIC16F628A doesn't work? |
 Posted: Mon Feb 13, 2012 1:36 am |
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Hi everybody! I'm very new to PIC programming. I've done my first projects with blinking LED's etc. a few days ago and it all worked fine.
Now I'm working on a new project where the PIC has to send MIDI messages to a MIDI DIN chassis.
The program starts with a delay of 1000ms, followed by sending the first midi messages in three bytes by using the putc() command, and a LED that turns on at pin A0. The putc transmit-pin is set to B2.
After another delay of 1000ms it sends another three bytes, and it turns the LED off. Then the program loops.
The LED is turning on and off like it should every 1000ms, but I'm not receiving any MIDI messages from the PIC. I'm sure the hardware part is hooked up fine and the problem is in the code.
The only strange problem I've encountered (also in my previous test projects) is that the PIC only works if I choose INTRC I/O as Osc while sending the HEX data to the PIC using a programmer.
Can someone please help me figuring out this problem?
The information on MIDI I've used so far comes from this article: http://alumni.media.mit.edu/~dmerrill/mas863/circuit.html
Thanks in advance 
The code:
| Code: |
#include <16F628A.h>
#use delay(clock=20000000)
#fuses HS, NOWDT, NOPROTECT, PUT, NOBROWNOUT, NOMCLR, NOLVP, NOCPD
#use fast_io(B)
#use fast_io(A)
#use rs232(BAUD=31250,XMIT=PIN_B2,RCV=PIN_B1,BRGH1OK)
// I've also tried the next line without success:
// #use rs232(baud=31250,parity=N,xmit=PIN_B2,rcv=PIN_B1,bits=8)
void send_3byte_midi_msg(char b1, char b2, char b3)
{
putc(b1);
putc(b2);
putc(b3);
}
void main()
{
disable_interrupts(GLOBAL);
set_rtcc(0);
setup_counters(RTCC_INTERNAL, RTCC_DIV_128);
set_tris_a(0x00); // make all A pins outputs
set_tris_b(0x00); // make all B pins outputs
while(1) {
delay_ms (1000);
send_3byte_midi_msg(0x80, 0x3C, 0x00);
output_high(pin_a0);
delay_ms (1000);
send_3byte_midi_msg(0x90, 0x3C, 0x7F);
output_low(pin_a0);
}
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Feb 13, 2012 2:34 pm |
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| Quote: | #use fast_io(B)
#use fast_io(A)
disable_interrupts(GLOBAL);
set_rtcc(0);
setup_counters(RTCC_INTERNAL, RTCC_DIV_128);
set_tris_a(0x00); // make all A pins outputs
set_tris_b(0x00); // make all B pins outputs
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You don't need any of the lines above to transmit bytes by #use rs232().
Remove them.
| Quote: |
The only strange problem I've encountered (also in my previous test
projects) is that the PIC only works if I choose INTRC I/O as Osc while
sending the HEX data to the PIC using a programmer.
|
Do you have a 20 MHz crystal and two 22pf capacitors installed in the
recommended circuit configuration, on the two oscillator pins of the PIC ?
If you can't make something simple such as a blinking LED loop, then
your crystal oscillator is not working.
| Quote: | | I'm sure the hardware part is hooked up fine and the problem is in the code. |
How do you know the hardware serial port connections are correct ?
And, how do you know that the Midi codes in your program will cause
the required action in your Midi device ? |
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FunkyLabRat
Joined: 13 Feb 2012
Posts: 10
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| Posted: Mon Feb 13, 2012 4:25 pm |
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| Quote: | Do you have a 20 MHz crystal and two 22pf capacitors installed in the
recommended circuit configuration, on the two oscillator pins of the PIC ?
If you can't make something simple such as a blinking LED loop, then
your crystal oscillator is not working. |
Gee, no wonder "the PIC only works if I choose INTRC I/O as Osc". I really thought the crystal Oscillators where included in the PIC itself 
I told you I'm a total beginner 
Do you know if it's possible to do what I want by using the INTRC_IO, or do I NEED an external Oscillator for RS-232 transfer?
| Quote: | | How do you know the hardware serial port connections are correct ? |
There are not much options (+5v, data pin and ground). Connected like this: http://devices.sapp.org/circuit/midi-out/
| Quote: | And, how do you know that the Midi codes in your program will cause
the required action in your Midi device ? |
I'm using MIDI-OX to monitor all incoming MIDI data.
Here's my updated code;
| Code: | #include <16F628A.h>
#use delay(clock=20000000)
#fuses INTRC_IO, NOWDT, NOPROTECT, PUT, NOBROWNOUT, NOMCLR, NOLVP, NOCPD
#use rs232(baud=31250,parity=N,xmit=PIN_B2,rcv=PIN_B1,stop=1,bits=8,BRGH1OK)
void send_3byte_midi_msg(char b1, char b2, char b3)
{
putc(b1);
putc(b2);
putc(b3);
}
void main()
{
while(1) {
output_high(PIN_A0);
delay_ms (1000);
output_low(PIN_A0);
send_3byte_midi_msg(0x80, 0x3C, 0x00);
send_3byte_midi_msg(0x90, 0x3C, 0x7F);
delay_ms (1000);
}
} |
Thank you for your time!! |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Feb 13, 2012 4:38 pm |
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You need to put the pre-processor lines in the correct order, as shown
below. Note how the #use delay() comes after the #fuses.
| Code: | #include <16F628A.h>
#fuses INTRC_IO, NOWDT, NOPROTECT, PUT, NOBROWNOUT, NOMCLR, NOLVP, NOCPD
#use delay(clock=20000000)
#use rs232(baud=31250,parity=N,xmit=PIN_B2,rcv=PIN_B1,stop=1,bits=8,BRGH1OK)
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If you do that, then you will get a helpful error message:
| Quote: | *** Error 99 Line 3(5,28): Option invalid Internal Osc Freq Wrong
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The internal oscillator can only run at 4 MHz on this PIC. You need to
edit the #use delay to this:
| Code: |
#use delay(clock=4M)
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If you do those two changes, the baud rate coming out of the PIC's Tx
pin should now be correct. It will match the value in your #use rs232()
statement and your program might now work. |
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FunkyLabRat
Joined: 13 Feb 2012
Posts: 10
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| Posted: Mon Feb 13, 2012 7:02 pm |
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Wow, that worked!
Thank you very very much, PCM programmer! You've saved me from many troublesome head-spinning days and nights 
Next step is figuring out how to add some buttons etc. |
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RoGuE_StreaK
Joined: 02 Feb 2010
Posts: 73
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| Posted: Tue Feb 14, 2012 8:40 pm |
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| FunkyLabRat wrote: | Next step is figuring out how to add some buttons etc.
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Don't forget to add a debounce routine, otherwise it may think you've sent multiple button presses. |
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FunkyLabRat
Joined: 13 Feb 2012
Posts: 10
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| Posted: Tue Feb 14, 2012 10:50 pm |
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| Quote: | | Don't forget to add a debounce routine, otherwise it may think you've sent multiple button presses. |
Thanks. I'd already thought about that, but I'm not sure how sensitive the buttons and transmitting will be. I'll try hooking up some buttons first (waiting for them to arrive in the mail) and will see for myself
Is hooking up multiple buttons on one pin using resistors totally safe? If there IS a chance it could fail under circumstances (room temperature etc.) I really won't use that option, but get a PIC with enough pins. |
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CodeSearcher
Joined: 03 Aug 2013
Posts: 1
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| Searched Code Found! |
| Posted: Sat Aug 03, 2013 4:25 pm |
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I've looking for this code some months! Thank you very much. I had found some codes or too much complex or for another compilers (Micro C, MPLab - Assembly).
The most interesting thing is the simplicity of this code.
It was because this code, that I registered myself to thank you.
_________________
I'm Just another brick on the wall.... versaopoetica.blogspot.com |
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