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Details

Non SD-Card usage

Install alsa-utils, OSS (?) and libportaudio2.

Add YOURSELF to the input group. The code uses a letter keyboard or usb numpad, if it exists.

sudo usermod -aG input YOURSELF

After logout and relogin YOURSELF you and miniMidiOut have the right to access keypad events (/dev/input/event0).

Start it

For sinus wave similar to a bell or flute:

miniMidiOut /dev/midi1 sin

For saw sound effect. It is the synth-sound from the 80th and similar to a spinet:

miniMidiOut /dev/midi1 saw

For square sound effect similar to 8bit arcade game from the 80th:

miniMidiOut /dev/midi1 sqr

For triangle sound effect similar to a cheap electric doorbell or gong:

miniMidiOut /dev/midi1 tri

For noise sound effect similar to wind, ocean waves or percussion:

miniMidiOut /dev/midi1 noi

After starting miniMidiOut with success, it plays 3 tones as startup theme.

miniMidiOut uses the default audio device for output. You can change this e.g. hw:1 with an optional 3rd miniMidiOut /dev/midi1 sin 1. The default is used with miniMidiOut /dev/midi1 tri -1.

miniMidiOut has an optional 4th parameter for the buffer size. The default is 16 and works well on Pi1. You can change the buffer e.g. to 512 with miniMidiOut /dev/midi1 sin -1 512 if you want.

There is an optional 5th parameter form -20 to 100 (fade). A negative value fades the sound of a key out WHILE it is pressed. With a value of -20 this sound is extreme short! Values form 0 to 100 changes the fade out AFTER the key is released. The default is 10.

You can set the envelope with a 6th optional parameter. The default value is 16000 and results in tone, where the first 16000 samples are a bit louder.

An optional 7th parameter is /dev/input/event0 as default. It is used to set the event device, which detects a pressed key on the Numpad.

You can set the samplerate with a 8th optional parameter. The default value is 44100. Some values may not work on your sound system an it will fall back to its own defaults.

Quit the application with CRTL + c or ESC.

Build

On debian or ubuntu you need these packages:

  • gcc
  • portaudio19-dev
gcc main.c \
    modus.c pseudo_random.c time_tools.c voice.c noise.c \
    device.c \
    device/keyboard.c \
    device/midi.c \
    player.c \
    globals.c \
    -Wall -Iinclude/ -lm -lportaudio -pthread -o miniMidiOut

Cmake alternative build

cmake -B .
cmake --build .

For a better handling with VisualStudio Code do this:

cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON .

Build system with buildroot (Pi1)

Check out my code as miniMidiOut-src and get/uncompress buildroot-2025.02.9.tar.gz:

git clone https://github.com/no-go/miniMidiOut.git miniMidiOut-src
tar -xzf buildroot-2025.02.9.tar.gz
cp -r miniMidiOut-src/pkg buildroot-2025.02.9/package/minimidiout
cd buildroot-2025.02.9/

Add this line into package/Config.in e.g. in the menu Audio and video applications:

	source "package/minimidiout/Config.in"

Add this line into linux/linux.hash:

sha256  7d6103116287f4823ced85ad06c942c6d64248fc9ce60dd47cbf0cbfb71ad456  linux-cip-6.1.157-cip48-rt26.tar.gz

Use my config file and start menuconfig:

unset LD_LIBRARY_PATH
cp ../miniMidiOut-src/pi1/buildroot.config .config
make menuconfig

Change nothing and save as .config.

make linux-menuconfig

Change nothing and save as .config.

then do (again):

cp ../miniMidiOut-src/pi1/kernel.config output/build/linux-custom/.config
make linux-menuconfig
make

Build bootable sd-card (Pi1)

The upper description creates a rootfs.cpio.gz with the complete root filesystem. You can use this file instead of an ext4 root filesystem on your sd-card. The system will work in a copy of that filesystem, which is placed in the RAM. The system will never write something (back) to the sd-card!

  • make a single msdos/fat32 partition (minimum 53MB) on your sd-card
  • copy to that partition...
    • the 4 output/images/bcm2835-rpi-* files
    • the file output/images/rootfs.cpio.gz
    • the linux kernel output/images/zImage
    • the content of output/images/rpi-firmware/
  • do not forget to copy the overlays folder inside output/images/rpi-firmware/

Hints for buildroot

if code changed:

make minimidiout-dirclean

or

make minimidiout-rebuild

and then do just make again and copy the new output/images/rootfs.cpio.gz to the sd-card.

Build system with buildroot (eeepc)

tar -xzf buildroot-2025.02.9.tar.gz
git clone https://github.com/no-go/miniMidiOut.git miniMidiOut-src
chmod +x miniMidiOut-src/eeepc_4G_701/rootfs-overlay/etc/init.d/S99minimidiout
cp -r miniMidiOut-src/pkg buildroot-2025.02.9/package/minimidiout
cd buildroot-2025.02.9

Add this line into package/Config.in e.g. in the menu Audio and video applications:

	source "package/minimidiout/Config.in"

Add this line into linux/linux.hash:

sha256  7d6103116287f4823ced85ad06c942c6d64248fc9ce60dd47cbf0cbfb71ad456  linux-cip-6.1.157-cip48-rt26.tar.gz

Use my config file and start menuconfig:

unset LD_LIBRARY_PATH
cp ../miniMidiOut-src/eeepc_4G_701/buildroot.config .config
make menuconfig

add/check this:

  • Target options
    • Target Architecture: i386
    • Target Architecture Variant: i586 (or i486)
  • System configuration
    • () Root filesystem overlay directories: set to ../miniMidiOut-src/eeepc_4G_701/rootfs-overlay
  • host utilities
    • deselect qemu
  • bootloaders
    • syslinux
      • mbr
make linux-menuconfig

add/check this:

  • Device Drivers
    • Sound card support
      • <*> Advanced Linux Sound Architecture
        • [*] Enable OSS Emulation
          • <*> OSS Mixer API
          • <*> OSS PCM (digital audio) API
        • <*> Sequencer support
          • <*> OSS Sequencer API
        • [*] USB sound devices
          • <*> USB Audio/MIDI driver
        • HD Audio
          • <*> HD Audio PCI
          • [*] Build hwdep interface for HD-audio driver
          • <*> Build Realtek HD-audio codec support

or cp ../miniMidiOut-src/eeepc_4G_701/kernel.config output/build/linux-custom/.config

Do the build, now:

make

If something went wrong, this build makes sometimes sense, too:

make host-fakeroot-rebuild
make host-genimage-rebuild

Build bootable sd-card (eeepc)

Build bootable sd-card in /dev/mmcblk0 as root user:

parted /dev/mmcblk0 mklabel msdos
parted -a optimal /dev/mmcblk0 mkpart primary fat32 1MiB 53MiB set 1 boot on
mkfs.vfat -F 32 /dev/mmcblk0p1

syslinux --install /dev/mmcblk0p1
dd if=output/images/syslinux/mbr.bin of=/dev/mmcblk0 bs=440 count=1

mkdir -p /tmp/mmc
mount /dev/mmcblk0p1 /tmp/mmc

cp ../miniMidiOut-src/eeepc_4G_701/syslinux.cfg /tmp/mmc/
cp output/images/bzImage /tmp/mmc/
cp output/images/rootfs.cpio.gz /tmp/mmc/

umount /tmp/mmc

You find mbr.bin, rootfs.cpio.gz, bzImage and syslinux.cfg in the release files.

Debugging

lsmod | grep snd
ls /dev/snd
dmesg | grep -i audio