Building the MeeBlip Firmware on Mac OS X

Here’s how you can build the Meeblip firmware on Mac OS X. For Windows, AVR Studio can be used to build the firmware. For Mac OS, the command line tool avra can be used, and presumably this will also work on Linux, although I’ve not tried this. Using avra to build the firmware was discussed on the MeeBlip forum, but I’ve summarised the steps below. This also includes the step to download the firmware to the MeeBlip microcontroller using the Sparkfun Pocket AVR programmer and avrdude. Full instructions for downloading the firmware can be found on the MeeBlip firmware page.
1. Download and build avra for Mac OS X and add it to your path
2. Install avrdude (one easy way is using Macports)
3. Locate the library file m32def.inc in avra (in avra-<version>/includes/) and copy it to your meeblip source directory containing meeblip.asm
4. Run the c pre-processor on m32def.inc to remove #define etc:
    cpp -P m32def.inc > temp
    mv temp m32def.inc
5. Remove the long comment in m32def.inc on line 465 as it is not compatible with avra.
6. Remove all comments (at the end of lines starting with a semi-colon) from meeblip.asm starting with a \ following the comment semi-colon and zero or more spaces as they are also not compatible with avra (these will be removed from future versions of the source). For example, remove comments from the end of the lines that have any of the following semi-colon backslash combinations below: 
  ;\
  ; \
  ;  \
  ;   \

7. Assemble the meeblip source with: 

    avra meeblip.asm
8. Download the assembled hex using avrdude: 

    avrdude -c usbtiny -p m32 -U flash:w:meeblip.hex

If you’re using a different programmer, you may need to replace the avrdude -c option with the one for your programmer. Here’s a picture of how the Sparkfun Pocket AVR Programmer should appear connected to the MeeBlip:

MeeBlip synth circuit board with Sparkfun Pocket AVR Programmer connected
Meeblip 1.31SE board with a Sparkfun Pocket AVR Programmer connected. Note the orientation of the connector, with the wires facing away from the audio and MIDI ports.

Meeblip DIY Kit Build

My Meeblip DIY kit is now built and making noise!
Meeblip synth kit

The hardware of the Meeblip is perhaps about as simple as a digital synth could possibly be: a microcontroller (with a good number of switches and knobs connected it), a MIDI interface to get notes in, a digital-to-analog convertor, and just enough audio circuitry to get sounds out. All the subtractive synthesis is done in the microcontroller, so it sounds like a simple soft-synth plugin. Except of course it lives in its own hardware, where the audio output circuit seems to add a bit of pleasing grunge to the sound.

Reflex Audio/CDM are steadily developing new versions of the Meeblip. The circuit board of this one is revision 1.31 SE which has some changes to previous versions: it’s now red, has a power switch, there is no USB power, and the connectors are mounted on the bottom to make positioning a front panel easier. There’s no case with the DIY kit (the quick build kit has a case), although there’s the option of the new SE case becoming available at the end of August, or even a home brew case…

The build instructions are easy to follow, although they are yet to be fully updated for the 1.31 SE board. So if you have a go at building this revision, one gotcha is that in order to check the power (step 3), all the power supply components need to be soldered in first, including the power diode, regulator and new power switch. One other thing to note is that the Meeblip needs a good low-noise external power supply, otherwise it can get some hum on the audio.

MeeBlip Hackable Synth

Meeblip open source synth

The MeeBlip is an open source hardware digital synth that was designed by James Grahame of Reflex Audio in collaboration with Peter Kirn of Create Digital Music.

The MeeBlip is designed to be hackable – easily modified to change the way it works. The MeeBlip seems like a good starting point for developing my own hardware synth projects so I ordered a kit to build with a view to doing some hacking…