Twin Tweaks ...
AN EXPANSION BOARD FOR THE NEXT EVOLUTION.
PROGRAMMING THE MARK III VIA USB.
beyond checking the designation of the COM port by the
programming software, further troubleshooting can be a
murky affair. Also, with his mechanical engineering
background, Evan is generally inclined to chalk up
unforeseen problems to the software side.
Thankfully, the immortal conflict between the
mechanical and software sides of a project did not play out
in this case, because the FTDI adapter worked just fine. We
were able to download programs just as seamlessly as
before, but without the middleman of our Keyspan adapter.
If anything, the end result of the project was almost a little
anticlimactic – no last minute troubleshooting, no epic
struggle against the knee jerk resistance to new USB
technology. Everything went according to plan, and we
were back to perfecting the Mark III’s line following
program in no time.
We had finally done it. We finished the journey upon
which we were side-tracked by a parts mix-up years ago.
We had conclusively proven that switching over a robotics
kit from an RS-232 connection to USB was no big deal. Or,
was it? The transition was simple and seamless – it only
took one part, as much soldering as you would be doing
anyway, and no headaches when trying to reconnect the
robot to the computer. Should this be ground shaking? It
demonstrates that there really is no good reason for
robotics kits to still come with RS-232 ports!
There were a lot of things that could have made the
conversion from RS-232 to USB less than ideal. Perhaps our
biggest concern was not the functional compatibility of the
new adapter regarding the actual communication between
the robot and the computer, but rather the physical
compatibility with the robot board and the adapter. The
Mark III board — as is to be expected from a robot with a
74 SERVO 09.2011
strong mini Sumo pedigree — is very compact and
doesn’t necessarily have the real estate to devote to
a bulky new connector. The FTDI folks had anticipated that
very concern, however, by mimicking the footprint of a DB9
Other potential snags included problems with the
device drivers or (on a more basic level) the design of the
adapter could have been much more of a burden for the
user to implement. The sleek casing of the unit
encompasses two major components: the USB-serial bridge
IC and the level shifters. Perhaps if those components could
only be acquired separately, it might be more of a chore to
implement them within the footprint of the DB9 connector
on a crowded PCB.
All of these things could have happened and might
give a semblance of a good reason as to why RS-232 ports
persist on so many robotics kits. However, none of them
did. The FTDI adapter is a simple-to-implement upgrade that
will let you ditch the middleman serial-to-USB cord in no
time. If only the folks that made the kits would take that
step instead of having the end users do it ...
The FTDI adapter itself will run you about $20, so from
a cost standpoint it is not necessarily a big advantage (or
disadvantage) compared to buying an adapter cord like the
Keyspan adapter that we’re fond of. That said, comparing
the cost to the user of modifying their own kit with the
cost to a company of using USB ports in the first place is
not an apples-to-apples affair. Kit producers have to include
some kind of port for connecting with the computer, and
we can’t see how there would be too much of a difference
cost-wise between the DB9 and USB Micro-B — particularly
when larger scale producers get the benefit of price breaks
associated with buying in bulk.
The great irony of this project is that out of all of the
kits that we have worked on over the years, the Mark III’s
retention of the RS-232 port is probably the least offensive.
The Mark III was developed by an independent robotics
group in the early aughts, back when using a DB9 connector