Over the past few weeks Rick Barnich KA8BMA has been doing some fine work on the schematic and PCB design for SmartMic. Yesterday Rick and I had a PCB and schematic review meeting over Skype, and Rick is now working on a few small changes. The PCB board layout will go in for manufacture this week by my good friend Edwin Chen from Dragino. I plan to be soldering the first prototype in early July.
Here is the current schematic, it would be helpful to have some more eyes on it to see if we have missed anything!
The design is now just 90 x 65 mm, so I feel we have achieved our PTT hand-held microphone form factor requirement. As the connectors are at either end of the PCB, it can also be mounted in a small box. Rick and his son are working on a 3D printed enclosure for the prototypes, we are undecided on the final enclosure.
Here is an image of the PCB, note the mechanical details showing the connector locations. Click for a larger version.
From my side I’m working on squeezing the FDMDV modem into the STM32F4 micro-controller. The main issue is run time memory, the high over sampling rate (M=160) means we are using too much RAM. No matter, I’ll re-arrange a few loops and trim that down a bit.