New 40MHz Open-Robot Controller Board

[abotics]

After much thought, I finally decided to support a 10MHz crystal on
the new controller board and also add a heart beat LED as well. With a
10MHz precision crystal the PIC18F4520 can be clocked at 40MHz when
the Phase Lock Loop (PLL) is activated. Overall both changes should
add less than $1 for the cost of components i.e. crystal, capacitors,
LED, and resistor.

I have already started to test out a 10MHz crystal with PLL on one of
my version2 PCBs and it should easy for me to make the necessary PCB
design changes for this and the heart beat LED. Once I make the PCB
changes, then I'll order a set of test boards from Express PCB and
perform the hardware testing to verify the changes. If I have time
I'll also verify a PIC18F4620 at 40MHz.

With the PIC18F4520 clocked at 40MHz I was able to set the UART baud-
rate up to 230,400 bps. This definitely speeds up the communication
and the process of wireless boot-loading. The increased clock also
speeds up floating point math routines which are used in the position
and velocity PID control routines.

I think these changes will be a great addition to the platform and
help those who are using Open-Robot as part of their robotics
research.

Regards, Abe

[abotics]

I uploaded a video from my cell phone and it shows Open-Robot driving
forward 16.0 inches under PID position & velocity control. The video
is under the Files section and is named "Open Robot Fwd.3g2". You will
need QuickTime Player to view this video. You can see two blinking
LEDs (1-red & 1-yellow) hanging out the side of Open-Robot. I only
intend to add one heart-beat LED to the new board, but for this
testing I was using two.

Abe

[abotics]

I made the necessary circuit board design changes so that the
controller board is able to support a 10MHz crystal & (2)-22pF Caps or
the existing 20MHz resonator. Not sure why someone would want to use a
slower, less accurate 20MHz resonator, but it will be an option. By
default I intend to ship boards with the 10MHz crystal and 22pF caps.
Also added a heart-beat LED that's connected to pin C1.

I've been thinking about whether or not the baud rate should be bumped
up from 115,200 to 230,400 bps. If we bump up the baud rate, then end-
users will not be able to use the XBee line wireless modules unless
they request a 115,200 bps boot-loader or are able to reprogram the
PIC18F4520 boot-loader themselves. I really like the 230,400 bps baud
rate because it uploads a new program very quickly. However, if you
are using a CCS ICD, then this probably does not matter.

The boards were ordered today and I expect to recieve them on
10/19/09. I hope there are no issues because the $85 cost does start
to add up fairly quick. After about 6 prototype board runs at $85 you
could have paid for a (100) board production run!

Abe

[abotics]

I just recieved the circuit boards from ExpressPCB and will begin the
assembly and test process. I hope to have these results by the start
of next week. Once these are verified and tested I hope to get a
production batch on order.

Abe

[abotics]

I just finished assembling the new board and everything looks great.
The new heart-beat LED is a very cool and functional addition.
Everything else appears to be functional as well. I have more testing
to perform before ordering a production run, but hopefully everything
goes well so I can get those on order. I posted a picture of the new
assembled board under the Files section and the file name is
"open_robot_controller_v2_final.jpg". I've pasted a link below.

http://open-robot.googlegroups.com/web/open_robot_controller_v2_final.jpg?gsc=5O2x2QsAAADYPvg4nkVzO65TNuqxyzBY

Abe

[abotics]

All testing was completed this weekend and I just ordered the first
production batch of the V2.1 boards. I expect to receive these by
11/11/09 and hope to have everything in place so that I can resume
shipping Open-Robot kits, but with the V2.1 board. I already started
to rework the Open-Robot Owner's Manual to reflect the design changes.
I am going to try and leave the kit price as it is today even though
I've added some cost with the +5volt RECOM regulator, 6-position RJ11
connector, Heartbeat LED, and the 2&3-position terminal blocks. Please
contact me through abe at abotics.com if you are interested in pre-
ordering a V2.1 Open-Robot kit.

At this time, I have not decided whether to leave the PIC18F4520 baud
rate at 115,200 bps or boost it to 230,400 bps. Raising it to 230,400
bps will not be compatible with the XBee line of wireless modules
since they max out at 115,200 bps. I really want to boost the baud
rate, so maybe we can offer two PIC18F4520 firmware versions: one at
115,200 and the other 230,400. Users can then specify which baud rate
they want.

Regards, Abe

[abotics]

I just received notification from ExpressPCB that the new PCBs have
shipped and should be here by the end of the week. I have several
other components on order from Mouser Electronics and they should be
here by the end of the week as well. Based upong this information I
should have kits ready for shipment by the end of next week at the
latest. I still need to go through the new Owner's Manual and make
sure there are no errors or typos. Most of the changes were image
related, but there were textual changes too.

On a similar note, I think I will leave the PIC18F4520 baud rate at
115,200 bps. Anyone who intends to purchase a CCS C PIC Compiler can
change the baud rate in source and recompile. I can post a compiled
hex file for the firmware that is 230,400 bps, but without modifying
the boot-loader you will always have to change the MatchPort b/g baud
rate back to 115,200 if you want to upload another version of firmware
and then change it to whatever the baud rate is for that specific
version of firmware.

Regards, Abe

[abotics]

Just received the new PCBs last night and they look great. I hope to
get kits assembled this weekend so that I'll be ready to start
shipping next week.

Abe