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Another idea to modify a MIDI merge with to_com I/O: add a MIDI output. Two I/O's, one at 38400, the other at 31250 bps. This would make a serial port to midi interface, also called baud rate converter, for those who can't or don't want to add USB/PCI/whatever MIDI interface, but have spare serial port. There is a serial MIDI interface driver for Linux in Ubuntu-Studio: see alsa.opensrc.org/index.php/Serial

Is there enough memory and processing power left in a PIC to add a software serializer and some flow control to the existing merge and software deserializer ?

Out of MIDIBox, there is another solution which I will evaluate too: the 8051-based serial interface from maxmidi.com . It will cost less for me (except for a bigger PCB) because I have recycled several 8031 + EPROMS 8)

Update: this interface design from yesteryears is a piece of crap, dead with only Win3.1/95 driver :P, there is no PCB, cheap power supply drawn from RS-232 lines, transistors and opamps instead of a true line driver/receiver like MAX235, complex 8031 code (software uart), hard to hack without source code... maybe well for mass production with low power x51 mpu, if able to be sold under $30, but not for DIY kits where part of the fun is in hacking, not buying programmed components.  I will redesign it with a second external uart.

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  • 6 months later...

I finished and test my first MM board :)

The downloaded firmware did not work with a PIC16F877A

(programmed with an universal programmer, not a cheap hack).

It was successful after editing midibox.h to add 'A' there:

#ifdef __16F877A  #include <p16f877A.inc> and rebuilding with

MPLab IDE.

The PCB layout has some mods:

-7805 laid down on copper side with tab contact to ground

-4 SMD leds and their resistors between PIC pins

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Glad it's working :) Would be cool to see pics of your board mods too!

It was successful after editing midibox.h to add 'A' there:

#ifdef __16F877A  #include <p16f877A.inc> and rebuilding with

MPLab IDE.

Thanks for this info! I have edited the code for the new (GPASM-based) toolchain according to this, I wonder if you would mind testing it for me, before I commit the source to SVN? I will email (or attach here or upload or whatever you like) the code with the hex files already built, and anything else that makes it easier for you :)

Thanks!

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  • 6 months later...

Sorry for late reply. I can test your hex file built with your toolchain as I have finished a second MM board and the programmer is still on. BTW I tried an HCPL2530 dual optocoupler instead of two 6N138's. It works with at least 2.7k pullup resistors.

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Something like this old PC, I have failed to multitask properly, sorry! I've had this tab open in firefox but I opened too many other tabs and it scrolled off the side and i forgot... My bad!

I'm doing it *right now*!

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Wiht a capital 'A' in the include filename, it returns this warning:

./16f/midibox.h:26:Warning [230] found lower case match for include filename
Fortunately the assembler is smart enough to just use the (silghtly) incorrect filename, but it still builds that way... Still, I thought it best to avoid it, so I hope you don't mind that I made a change:
#ifdef __16F877A
#include <p16f877a.inc>
#endif
Note the lowercase 'a', I guess this is a difference between GPASM and MPASM. I have confirmed that all versions of GPASM use this lowercase variant designator. The necessary change in the makefile to enable this, is:
midimerger_pic16f87x.hex: 16f/main.asm
	gpasm $< $(GPASM_FLAGS) -I ./16f -p 16f877a -o midimerger_pic16f87x.hex
Note that although I have used the lowercase 'a' here, the assembler is smart again and will create the define with the capital A regardless of which case you use here, so
midimerger_pic16f87x.hex: 16f/main.asm
	gpasm $< $(GPASM_FLAGS) -I ./16f -p 16f877A -o midimerger_pic16f87x.hex

Also works.

Anyway the hex:

Thanks for testing!!  :)

midimerger_pic16f87x.hex

midimerger_pic16f87x.hex

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