I introduced in another thread some nice features of NanoPi NEO Air board as an alternative to the Raspberry Pi. I mentioned in that post that I am working on a board that will stack onto the NanoPi NEO Air and will provide quad Dynamixel bus, power and IMU (9250 - accelerometer, gyroscope and magnetometer).
That time has come and I am pleased to show you the first (working) prototype of this board:
(The IMU is not yet soldered yet - but there will be soon. The reason is that the IMU-9250 chip is quite expensive and I wanted to make sure that the rest of the board works as expected before placing that in).
The board uses the FTDI 4232H in a new 56 VQFN package that allows the creation of 4 serial ports from one USB port. There is no need for new drivers - it is supported by the system out of the box.
The board also includes a 5V 1.5A switched regulator that powers the NanoPi board and has 2 connectors for each bus allowing you to easily hook up chains that otherwise would become too long (for example feet and torso, hands and head, etc.). The picture above is with XL connectors but there will be versions with AX/MX and XM/XH connectors too (only the TTL). I will think if would make sense to make a board with RS485 connectors - the chips and the connectors are significantly larger and I'm not sure they would fit on the board.
The board as mentioned earlier stacks up on the NanoPi and I used the female headers to fix the antenna needed for WiFi and Bluetooth:
To compare the whole ensemble with a Raspberry Pi here is a picture head to head:
The Raspberry Pi is 42 grams on its own and the whole ensemble including the NanoPi Neo Air, Heatsink and the Dynamixel board are 38 grams.
You can also see in the last picture that the add-on board exposes the second USB port that can be used to connect a hacked WiFi dongle (or other USB device) - without using bulky or heavy connectors. Here is a better picture:
I'm planning one the next week or so to put it through some stress testing to see how well it's performing. I need to change the chest design of my small Poppy to put it in.
If you have any suggestions for testing, please let me know.