WEEGEE development log

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spymongoose
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WEEGEE development log

Post by spymongoose » Mon May 05, 2008 3:49 pm

posts taken from http://tech.groups.yahoo.com/group/weegee_robot_board/ written by spymongoose
The most recent revisions of WEEGEE board files will be soted at the yahoo group as well as on http://www.shadowmite.com. These files will have the revision number in their title. Be sure that you are using the most up to date version. The 4 prototype boards are known as WEEGEE 1.0. Subsequent boards made after these will be known as WEEGEE 1.1. Check the shadowmite.com forums or the yahoo group to see what the latest revision is and be sure that your parts lists are for the same version.

originally posted 28 APR 2008 @ 10:23 AM
Welcome to the group!

Shadowmite and myself have put a lot of work into this hobby robotics
board, and while we are developing it for our own robotics needs and
interests we hope that it will be useful to other hobbists as well.
The board is in the final design stages and we are just about ready to
have 4 prototype boards made. The board was designed in the free
version of eagle (http://www.cadsoft.de/). This board is being
designed by hobbists, for hobbyists.

I will post here as new information becomes availiable.

originally posted 28 APR 2008 @ 1:32 PM
xtal frequency 7.3728mhz


We have decided on using an external oscilator clocked at 7.3728MHz to
facilitate optimal use of our USART to the xbee radio. The USART
wants to use mutiples of 1.8432MHz (4 x 1.8432 = 7.3728) falling
withing the maximum limits of our atmega32l's maximum frequency of
8mhz. We have selected the HC-49S crystal from mouser, mostly because
its the smallest through hole crystal we could find, and the datasheet
reccomends using 20pf caps with that crystal. These additions were
added to the board design.

originally posted 29 APR 2008 @ 11:55 AM
status update apr 29 2008


The board traces got the last finishing touches today, and Matt has
submitted the design to the PCB house. The return image from the PCB
house was uploaded in the photos section. The design was modified
slightly to make some traces more rounded, but for the most part thats
how the 4 prototypes will look.

The spreadsheets containing the pinouts and the parts lists are made
and checked by both Matt and myself and have been uploaded to the
files section.

I have taken on the job of putting toether a rough draft of the manual
including the board assembly instructions and the board tests that
should be done while it is going together. I am doing this because
its similar to every other custom assembled board manual I have seen.

originally posted 30 APR 2008 @ 1:51 PM
status update apr 30 2008


We heard back from the board house, the overall size of the prototype
boards will be 3.649 x 3.027 inches.

There was some discussion on how to properly heatsink the motors. We
have borrowed the H-bridge design from
http://www.mcmanis.com/chuck/Robotics/t ... ridge/bjt-
circuit.html and we used tip107's and tip102's, both capable of 80
watts when cool. While niether myself nor matt intend on using the 80
watt x 2 rating to capacity (my target motors are run at 3.7 volts at
a stall current of 2 amps x 2 motors = 14.8 watts at stall, Matt plans
on running his robot at 12 volts x 2 amps x 2 motors = 48 watts at
stall) no heatsink we design can properly handle much of what we want
for very long. Clearly we intend on using a thermister and an analog
input as a temperature sensor on the heatsink or take feedback from
wheel encoders to prevent stall conditions, it will be upto the end
user to monitor thier motors to prevent stalls and excessive heat
buildup.


originally posted 1 MAY 2008 @ 12:58 PM
status update may 1 2008


I ordered parts of 2 complete 1.0 weegee board today, in anticipation
of getting the protoype boards back from the PCB house. I also
ordered 3 1mw xbee's with the chip antenna and the usb to xbee board.

There was some talk of implementing a camera modual, and it was
decided that the popular avr-cam would be the best solution. Part of
that decision was that we wanted to do a bulk of the vision processing
on a seperate avr and let the WEEGEE control the autonomous parts of a
robot, IE the radio link and the motor control and let the user decide
how much more high level decision making the onboard atmega32l would
do without being burdened by the load of vision based processing. By
using this solution, the WEEGEE can take advantage of off board vision
based processing where the camera becomes little more than a sensor
rather than the primary decision making device. Again, its upto the
end user to decide how to implement his or her sensors into his or her
programs.


originally posted 5 MAY 2008 @ 1:51 PM
status update may 5 2008


We have uncovered a few hardware bugs, namely the resistors in the
hbridge network were calculated for a 5v input and did not work
properly at 3.3v. Some resistor values have been changed. Other
changes include a misrouted pin to the xbee (why do they have 2 sleep
pins when only one works?) that was routed to xb pin 13 is now routed
to xbee pin 9, or the S2 pin 6 that is connected to xb pin 9.

Additional changes we are making for the 1.1 board is an upgrade to
the atmega644v-10n chip, having double the ram and program space and 2
uarts. The prototype boards will have to be modified to use both
uarts, however the 1.1 boards will have the second uart pinned out to
the edge of the board.

Other potential changes may include a modification of the isp header,
as one xbee radio died a tragic death because 5 volts from an avr
programmer fried it through the vcc pin on the isp header. We may
dissconnect that pin from use or diode protect it as the board was
meant for external power use anyway.
Talkabout T900 --> Handspring Visorphone --> Kyocera 7135 --> Treo 600 --> Apache PPC 6700 -->Nokia 770
http://www.shadowmite.com http://www.ppc6700users.com

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Re: WEEGEE development log

Post by spymongoose » Wed May 07, 2008 4:14 pm

Image
I have uploaded the new picture of the WEEGEE 1.1 board, although we
have no intention of producing any untill we need to. The prototype
boards have been modified to better suit our uses, and these changes
have been reflected in the 1.1 design. The changes are as follows.

1. The VCC pin on the ISP is no longer connected to VCC. It is not
connected to anything. This is done so that +5v from AVR progammers
do not fry the voltage sensitive Xbee radios. Power during
programming is still applied from the board's regulator and the +3.3v
logic is enough to register as a +5v logic high.

2. The AVR has been changed to the ATMEGA644PV-10PU family to make
use of double the amount of ram and program space found on the
ATMEGA32.

3. The ATMEGA644 has 2 UARTS, UART1 (PD0, PD1) is still pinned out at
the Xbee radio's TX/RX pins, UART2 (PD2, PD3)is pinned out at a
serial port at the edge of the board. UART1 is also acessable by 2
via passthroughs on the board, near the serial port and radio.

4. The Xbee RSSI pin is no longer pinned directly to the AVR, rather
it can be acessed by the user at S2 pad 3

5. The Xbee SLEEP pin is now attached to PD5, moved to allow use of
UART2.

6. The pinout order of S1 and S2 have been changed to allow a better
trace layout on the board. See supplementing documentation for the
new pinout order.

7. PD7 going to the LED is now acessable by a jumper block. This
allows users to acess the LED by other I/O pins, freeing up PD7 for
additional use. A jumper connects the LED to PD7 for normal use.

8. PD6 going to the piezo is now acessable by a jumper block. This
allows users to acess the piezo by other I/O pins, freeing up PD6 for
additional use. A jumper connects the piezo to PD7 for normal use.

9. The drill hole sizes for SW1 and the piezo were enlarged slightly
as these components were a very tight fit on the 1.0 boards.
Talkabout T900 --> Handspring Visorphone --> Kyocera 7135 --> Treo 600 --> Apache PPC 6700 -->Nokia 770
http://www.shadowmite.com http://www.ppc6700users.com

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Shadowmite
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Re: WEEGEE development log

Post by Shadowmite » Wed Apr 22, 2009 12:44 pm

Weegee 1.1 is finally complete. The project files can be found at:
http://www.shadowmite.com/temp/weegee1.1.rar

In addition to the previous mentions I also added a microsd slot to have memory available in bulk via the SPI interface. Also decided not to cut the ISP power pin out as the programming standard does require it to be "by the book". So just make sure you use a high enough quality programmer that it doesn't put 5v out all the time. Even better, find one that can do 5/3.3/none selectable... :)
---
Shadowmite

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