Modding my Monotron Delay

Monotron Mod

I made a first attempt at adding CV in and an external power supply to a Korg Monotron Delay:

For the power I simply used an external power bank and connected 5V and GND to the respective pins on the Monotron.

5v and GND on the Monotron Delay

The 5V CV signal from the Korg SQ-1 goes into the gate pad on the Monotron. It kind of works, but tuning is quite tempera(ture)mental.

GND and gate pads on the Monotron Delay

Apart from temperature the pitch is directly dependent on the Monotron’s supply voltage, so I would either need to step down the USB voltage to ~3V and make use of the boost converter that is built into the Monotron to get 5V, or use a higher voltage power supply and regulate it down. Any idea what’s better?🤔

TM1638 LED&KEY based MIDI visualiser on the Raspberry Pi Pico

MIDI visualiser

This evening I had some fun with @diyelectromusic‘s SimpleMIDIDecoder MicroPython library and the TM1638 LED&KEY module. The display shows MIDI channel and note number and the LEDs light up depending on velocity.

This is running on the Raspberry Pi Pico and also requires mcauser’s TM1638 library.
Here’s the (slightly rushed) code:

# MIDI note visualiser for Raspberry Pi Pico and TM1638 LED&KEY module by @AxWax
# Demo:
# This is heavily based on and requires
# the SimpleMIDIDecoder library by @diyelectromusic, which can be found at
# as well as the MicroPython TM1638 LED Driver library by mcauser from
# Wiring:
# serial midi input on GP1 (UART0 RX)
# TM1638 Pico
# VCC 3v3
import machine
import time
import ustruct
import SimpleMIDIDecoder
from time import sleep_ms
from machine import Pin
import tm1638
# Initialise the LED & Key
tm = tm1638.TM1638(stb=Pin(4), clk=Pin(3), dio=Pin(2))
# Initialise the serial MIDI handling
uart = machine.UART(0,31250)
# MIDI callback routines
def doMidiNoteOn(ch, cmd, note, vel):"C."+str(ch)+" N."+str(note)+" ")
if vel == 0:
elif vel <= 16:
elif vel <= 32:
elif vel <= 48:
elif vel <= 64:
elif vel <= 80:
elif vel <= 96:
elif vel <= 112:
def doMidiNoteOff(ch, cmd, note, vel):
tm.leds(0b00000000)"C."+str(ch)+" N."+str(note)+" ")
def doMidiThru(ch, cmd, d1, d2):
if (d2 == 1):
md = SimpleMIDIDecoder.SimpleMIDIDecoder()
md.cbNoteOn (doMidiNoteOn)
md.cbNoteOff (doMidiNoteOff)
md.cbThru (doMidiThru)
# the loop
while True:
# Check for MIDI messages
if (uart.any()):[0])

Displays on the Raspberry Pi Pico

1602 LCD with Raspberry Pi Pico

I spent longer than I care to admit on failing to get either a TM1638 LED, an SH1106 OLED or a 1602 LCD to work with my Pico. Turns out one of my jumper wires had an intermittent fault 🤦
After a wire transplant everyone is finally happy!

Kevin the MQTT Owl

Kevin started his life when my then flatmate found him in a bargain bin for 25p. Once the inbuilt button cell battery had depleted she let me have a play with it.

I removed the battery holder, rewired the eye LEDs, built a circuit board consisting of an ESP8266 and a DFPlayer Mini MP3 Player and hot-glued a speaker where the battery holder used to be.

Initially I simply hooked him up to our doorbell, whose 433MHz signal gets converted into MQTT messages through Sonoff’s RFBridge running the excellent Espurna firmware: