I've used the piezo transducer from the NerdKit to make a drum trigger, the intention being to send appropriate midi messages to a drum synth to make a sound when I hit the transducer.

I've got the trigger part working nicely, I can light an LED by tapping the transducer. But when I try to send out midi data I get absolutely zilch.

I've pieced together the code below from various sources, and the hardware is just a midi socket on piece of stripboard, with header pins so I can plug it into the breadboard.

The midi socket's pin 4 is connected directly to the ATMega168's TX pin, pin 5 is connected via a 220R resistor to +5v.

I know the midi cable is good, when I unplug it from Nerdkit and connect it to the midi out socket of my roland synth I can play notes and hear drums from the drum synth. When I connect it back to the Nerdkit, back to zilch again.

Can anyone help me please?

Source code (with the boring buts cut out):

#define F_CPU 14745600

#include <stdio.h>
#include <stdbool.h>
#include <stdlib.h>
#include <inttypes.h>
#include <avr/pgmspace.h>
#include <avr/io.h>

#include "../libnerdkits/delay.h"
#include "../libnerdkits/lcd.h"
#include "../libnerdkits/uart.h"

#define TRUE 1
#define FALSE 0
#define MIDI_BAUD 31250

void midiInit(bool out, bool in)
{
    // Set baud rate to 31250
    uint8_t midiUBRR = (uint8_t)(F_CPU/16.0f/MIDI_BAUD); // = 29;
    UBRR0H = (uint8_t)(midiUBRR   >> 8);
    UBRR0L = (uint8_t)(midiUBRR & 0xFF);
    if(out)
    {
        // Enable transmitter
        UCSR0B |= (1<<TXEN0);
    }
    if(in) 
    {
        //Enable receiver
        UCSR0B |= ((1<<RXEN0) | (1<<RXCIE0));
    }
    //Set frame format: Async, 8data, 1 stop bit, 1 start bit, no parity
    UCSR0C = (1<<UCSZ01) | (1<<UCSZ00);
}

void sendmidi(uint8_t databyte)
{
    while ((UCSR0A & (1 << UDRE0)) == 0); // Do nothing until UDR is ready for more data to be written to it 
    UDR0 = databyte; // Send out the byte value in the variable "databyte"
}

int main() 
{......................

    while(1) 
    { 
        // get sample
        trig_sample = adc_read();

        if(trig_sample>0)
        {
            is_trig = TRUE;
            PORTB |= (1<<PB1); // LED ON
            sendmidi(0x90); // note on, midi channel 1
            sendmidi(0x3C); // C3
            sendmidi(0x7F); // max velocity (127)

            if(trig_sample>last_trig_sample)
            {
                last_trig_sample = trig_sample;
            }

            delay_ms(50);
            sendmidi(0x90); // note on, midi channel 1
            sendmidi(0x3C); // C3
            sendmidi(0x00); // min velocity (0)

        }
        else
        {
            is_trig = FALSE;
            PORTB &= ~(1<<PB1); // LED OFF
            last_trig_sample = 0;
        }

    }........

Sorry, messed up the image url!

re: image URL

Here is what Google says about it:

403. That’s an error.

Your client does not have permission to get URL /Fggx8o8Bgi7vz-NrwHgooes746gD8Ntb71RA7VGHe2ow3Oj69E4DAePuSKFRJRdP5aMyzdVXd94 from this server. (Client IP address: 24.45.153.118)

Forbidden That’s all we know.

Ralph

Sorry about that - I uploaded the image using Google Drive, and I changed the share settings to 'anyone who has the link'. Guess I'll have to find somewhere else to host the image. Check back later...

I think this is should work...

And here's the trigger circuit: