Griff and Griff Mini - self-build 384kHz USB microphones
for bat detection and recording
Griff and Griff Mini are powered by the Raspberry Pi Pico, and are extremely inexpensive - either design can be built for under £5 per device when building 10-off. Griff Mini is a more "sensible" shape and features mounting holes at the corners to simplify attaching permanently to a surface or to a hat. Griff, the original design, is just too cute for words and features an integral brooch pin for instant wearability. Functionally and electrically the two designs are identical, but Griff Mini has a somewhat less cramped layout, and as a result has the potential to deliver slightly cleaner recordings, but this has not been tested and any differences will be negligible.
Blank PCBs and solder paste stencils are available from PCBWay at a cost of $5 for 10 PCBs, $10 for the solder paste stencil, plus shipping, which is typically additional $24 for shipping to UK : https://www.pcbway.com/project/shareproject/Griff_Mini_d4d7cbaa.html
The electronic components needed to build Griff and Griff Mini are available direct from DigiKey : the DigiKey link is on the PCBWay page, along with a link to the brooch pin I use on the back to make the designs wearable.
Note that your build costs can be dramatically reduced if you buy Raspberry Pi Pico clones from AliExpress, rather than genuine Raspberry Pi devices. You can save around £2 per assembled device by taking this route : https://www.aliexpress.com/w/wholesale-raspberry-pi-pico.html, and these clones ofer other advantages in that you can choose a USB-C connector rather than just micro USB. The choice of USB-C offers additional indirect cost saving, as this allows you to use either USB-C to USB-C cables, which have recently become much cheaper than legacy micro USB cables, or even a very short, rigid USB-C to USB-C male-to-male connector : just search for "USB C male to male adapter" on your local Amazon. The adapters can usually be found for under £8 for a pack of 2.
The build for these designs is very easy. The only fiddly component is the Syntiant microphone chip which is very small, and you need to be careful when assembling that you have not accidentally squeegeed solder paste into the acoustic hole through the PCB. Build time per Griff is well under 10 minutes once you are in the swing. I offer as proof an 8 minute build video for a Griff Mini of the current design. It is presented without edits, so every ham-fisted, time--consuming misstep and dropped / forgotten component is included - enjoy 😀
Blank PCBs and solder paste stencils are available from PCBWay at a cost of $5 for 10 PCBs, $10 for the solder paste stencil, plus shipping, which is typically additional $24 for shipping to UK : https://www.pcbway.com/project/shareproject/Griff_Mini_d4d7cbaa.html
The electronic components needed to build Griff and Griff Mini are available direct from DigiKey : the DigiKey link is on the PCBWay page, along with a link to the brooch pin I use on the back to make the designs wearable.
Note that your build costs can be dramatically reduced if you buy Raspberry Pi Pico clones from AliExpress, rather than genuine Raspberry Pi devices. You can save around £2 per assembled device by taking this route : https://www.aliexpress.com/w/wholesale-raspberry-pi-pico.html, and these clones ofer other advantages in that you can choose a USB-C connector rather than just micro USB. The choice of USB-C offers additional indirect cost saving, as this allows you to use either USB-C to USB-C cables, which have recently become much cheaper than legacy micro USB cables, or even a very short, rigid USB-C to USB-C male-to-male connector : just search for "USB C male to male adapter" on your local Amazon. The adapters can usually be found for under £8 for a pack of 2.
The build for these designs is very easy. The only fiddly component is the Syntiant microphone chip which is very small, and you need to be careful when assembling that you have not accidentally squeegeed solder paste into the acoustic hole through the PCB. Build time per Griff is well under 10 minutes once you are in the swing. I offer as proof an 8 minute build video for a Griff Mini of the current design. It is presented without edits, so every ham-fisted, time--consuming misstep and dropped / forgotten component is included - enjoy 😀
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A finished USB-C Griff Mini, assembled as a werable device with integrated brooch pin
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When using Griff as a USB microphone for bat detection and recording on a mobile device, the recommended apps are Android : Bat Gizmo (by John Mears) on the left, and on the right for iPhone and iPad : Bat Detector (by Phil Atkin - that's me by the way 😀 👍)
Bat Detector features real-time time expansion along with auto-tuned heterodyne detection, and saves a folder of sonograms along with your 384kHz WAV recordings for rapid visual scans. Bat Gizmo features twin heterodyne detection, manually tuned. Both apps embed geolocation into their WAV files using GUANO metadata, and generate recordings optimised for the BTO Acoustic Pipeline. |
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On the left is the help file for Bat Detector for iPhone and iPad. This PDF is in fact embedded witin the app, but it's here because people seem to have trouble finding it :)
Look in - Files -> On my iPhone -> Bat Detector How to flash new firmware onto the Pico 
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So why is a bat detecting microphone called Griff?
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Griff is named after a superstar Noctule, the mealworm-munching star of the TV campaign for a major Hollywood movie featuring the dashing Robert Pattinson in a cracking Bat Suit. But beyond that he was the best bat that ever was. He was an educational bat looked after by the lovely Amy, he charmed hundreds of visitors to the launch of "On a Wing and a Prayer" at St. Sampson's church Cricklade, and after a very happy and rich life he passed away in July 2025. Griff will never be forgotten, and we all loved that guy.
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