drag race (see the April ‘09 issue for more) or
tipping over glittery ramps in the Cirque du
Robot (January ‘ 11), we have enjoyed using the
Mark III as a sometimes hapless foil for our
Most of the tasks we have enlisted it for
have played to its strengths like line following
around a track. Other times, we have deliberately
taken advantage of its Sumo inspired low ground
clearance, and in the Cirque du Robot we were
still surprised at how high and steep we had to
make our ramp obstacles so that they would tip
over the low-riding bot. No matter whether we
used the Mark III as a ringer, a tomato can, or
something in between, we think it is impressive
in the sense that it has remained a viable
competitor in featured projects over the years.
The Solution To The
THE BOARD OUTFITTED WITH THE FTDI ADAPTER.
The inspiration for this upgrade to the Mark
III kit actually came from SERVO Magazine itself. The FTDI
adapter necessary to convert an RS-232 kit to USB was
featured in the August ‘ 10 issue in the Robytes section. The
mod USB RS-232 embedded retro DB9F — as it was
officially designated in the Digi-Key catalog — looked like
the perfect solution to the persistence of the RS-232 ports.
It was compact, soldered directly to the PCB through holes,
and it was affordable. A single unit costs about $22. The
FTDI adapter was designed specifically to upgrade devices
still relying on the quaint DB9 connector, and this explains
its somewhat bulky appearance when compared to USB
ports we all know and love. The FTDI adapter was designed
to avoid compatibility problems with the existing PCB, and
so it mimics the footprint of the DB9 connector.
On the technical side, the FTDI adapter
includes the FTDI FT232R USB-serial bridge IC
within the unit, along with the requisite level
shifters, so implementing the adapter is really a
matter of plug and play. There are a few historical
caveats, however, and they are candidly laid out
in the datasheet provided by FTDI for the adapter.
The familiar DB9 pinouts are the result of the PC-AT standard introduced by IBM in the early 1980s.
Not every single device adopted the standard,
though after this many years it is exceedingly
unlikely that anyone using the adapter will be
foiled by nonstandard pinouts. The FTDI adapter
uses the standard pinouts, as we expect would
be the case with whatever robot kit you feel like
bringing into the modern age.
It would have been easy enough to desolder
the DB9 connecter and replace it with the FTDI
adapter, but we wanted to build up a new board
anyway and this would allow for more visually
stunning side-by-side comparisons. The FTDI
adapter did indeed retain the footprint of the DB9
connector, and thus avoided any problems with running
into the ICs and capacitors that crowded the PCB.
FREE FROM RS-232 AT LAST!
SERVO 09.2011 73