I finally got the boards in my hands and soldered and tested one board. It works as it is supposed to, but still has little things I want to fix in the next revision. Here are some pictures:
Highlights:
- ATmega328P DIP28 package (yellow rectangle) mounted in a socket to be easy replaced
- SN754410 dual H-bridge (purple rectangle) with 1A continuous current draw per motor (2A peak)
- screw terminals for motor connection (green squares)
- correct hole placements and female headers to fit the Arduino Diecimila perfectly
- extended the board on the left side so the sensor and servo connectors do not interfere with any shieds
- replaced the bulky 220uF capacitors with lower profile 100uF capacitors so they fit under the shields
- installed the 5V 3A voltage regulator flat on the board with the hole aligned to the mounting hole of the board (red square at the top of the board)
- a 3.3V 250mA voltage regulator to power off sensors that need that voltage (pink square at the bottom of the board)
- added a second power switch for the motors and servos (brown rectangle at the top of the board)
- 6 connectors for servos (top left corner), with Ground (black), Voltage (orange), Signal (yellow) pins
- 6 connectors for sensors (bottom left corner), with Ground (black), 5V (red), Signal (yellow) pins
- jumper J1 to select the power for the servo connectors either 5V (shunt in red rectangle position) or battery voltage (shunt in orange rectangle position)
- jumpers J2 and J3 to select the control mode for the motors, either 2 signal pins (shunt in black rectangle positions) or 3 signal pins per motor (shunt in grey rectangle positions) with the loss of 2 control pins for servos
- relocated the reset button (light green rectangle) to the upper right corner, close to the edge of the board
- ISP header for hardware programmer (blue rectangle)
- relocated FTDI header (dark blue rectangle) at 90 degree for easy access from under a shield
- doubled the female headers with male headers perfectly spaced so you can build your own shield from a perf board or use wire jumpers for custom connections
Lowlights:
- the electronics power switch is hard to flip when under a shield
- the motor power switch does not fit between the jumper and voltage regulator on the board, I had to solder it sideways, but it may be a good thing. I will look into sourcing 90 degree switches
- the 3.3V regulator has to be mounted in reverse, wrong pad connections in Eagle
I guess third time is the charm, so the next revision of the board will have these issues fixed. Until then, look at how nicely the board fits my Compact robot:
Of course, I added the kit to the store here and have updated the Assembly Guide that you can download here.
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