Cheaper alternative to PIC18F2550

[roger]

Hi Dmitri,

Quick 2 questions please. If I use the circuit diagram at the top of this thread - PIC18F14K50 MIDI USB.PDF - and a programmed 14K50 per the same thread, and I feed a MIDI signal into the UART RX, will I get a USB signal out. If yes, and I then feed a USB signal, (say from MIDI-OX) into the 14K50, will I get a MIDI UART signal out?

(Sorry, but I do not understand the Megadrum system).

Thanks & Regards

Roger

[dmitri]

This is exactly what it does - converts UART into USB MIDI.

[roger]

Oh great, many thanks

Roger

[kooroshi60]

Hello dmitri

I wonder if I can substitute the PIC18F2550 with PIC18F13K50 and Connect the pins number 10 and 12 to the midi out and in circuit? Or it must go through the megadrum board to work?
Do these pins transmit and receive UART midi signals direcly? without intervention of megadrum board?

PIC18F2550 is so expensive here in Sicilia and I intend to replace the chip with 18F13K50 to build
the MIDI-USB interface with lower price.

Best regards
Ciao

[dmitri]

PIC18F2550 and PIC18F13K50 are not pin compatible so if you want to use PIC18F13K50 in a board made for PIC18F2550 you have to make sure to make connections according to differences between PIC18F2550 and PIC18F13K50 pinouts. You also need to make sure that you can program PIC18F13K50 because I only tested programming it with a PicKit2 programmer.

[kooroshi60]

Hello again Dmitri

I used the schematic and the firmware you had provided and built the Midi USB interface with a PIC18F14K50 mcu. Everything is OK but it can't send polyphonic notes ( Multiple sysex messages)
to the PC. Only one note at a time is being sent; in result, when I play harmonic melodies I hear them incomplete.I experienced same result with different PCs and VST software. I checked it with MIDIOX software and noticed that even when I play rapidly some notes become neglected. Seems like it's not fast enough to establish a 1-1 connection between the gear and PC. I used a 12MHz resonator and a 6N138 optoisolator.

Would you please tell me what can be wrong with it?
Best regards
Ciro

[dmitri]

I don't know but you are welcome to look at the source code.

[kooroshi60]

I wish I could! I'm not that professional. Previously I was using a Megadrum Midi-usb with PIC18F2550 and it was working perfectly with V2 firmware. I gave it to my friend; now I need to build one with 18f14k50... Thank you anyway.

[kooroshi60]

I was struggling with my interface for the whole evening. I checked every single part. every thing was cleanly in it's place, no solder paste, nothing... but I wonder why it works like this.
after all this is the firmware you have made and tested; the problem should be something else.
It seems like the MCU is not working with the correct frequency. Is 12MHz resonator the correct one?
Is it possible for you to make available on the website the firmware for PIC18F14K50 for other frequencies? especially for 20MHz crystal.

[dmitri]

I was struggling with my interface for the whole evening. I checked every single part. every thing was cleanly in it's place, no solder paste, nothing... but I wonder why it works like this.
after all this is the firmware you have made and tested; the problem should be something else.
It seems like the MCU is not working with the correct frequency. Is 12MHz resonator the correct one?

If the crystal frequency were incorrect, your PC would not even detect the device.

Is it possible for you to make available on the website the firmware for PIC18F14K50 for other frequencies? especially for 20MHz crystal.

You can take the source code and compile it for any frequency PIC18F14K50 and the firmware supports.