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From software algorithms to material selection, Mr. Roboto strives to meet you
where you are — and what more would you expect from a complex service droid?
This month, there is a mix of questions from sensors to
programming. I hope that you learn something new from
Mr. Roboto’s tower-top lab. Let’s dig in!
Q. Mr. Roboto, I have an Arduino Pro 328 using 5V power from SparkFun and a SparkFun FTDI Basic board that I use (over USB) to program it. When I
use my Arduino 017 setup, this works fine. But, when I try
to program the board using avrdude, it fails saying that
“The programmer is not responding.” What am I doing
avrdude -c arduino -p M328p -P
/dev/cu.usbserial-A700e5Jl -U flash:w:gen328.hex
After scratching my head, searching the Web, and
finally doing some of my own experimentation, I discovered
the problem. We (neither of us) didn’t specify the baud
rate. The SparkFun FTDI Basic board is a USB-to-serial
translator. The Arduino Pro (ATMEGA328p) expects data at
57600 baud. Try this invocation and your setup will work:
— David (via email)
A. David, You didn’t say how you were invoking avrdude, so I put together a sketch for the Arduino IDE and indeed it worked. I then used avr-gcc to
create a simple LED blinker and tried to use avrdude to
program my Arduino Pro board (see Figure 1 for my layout)
and sure enough, it failed for me. I started with this
invocation to program the board:
Avrdude -c arduino -p M328p -P
/dev/cu.usbserial-A700e5Jl -b 57600 -U
Figure 1. Arduino Pro with FTDI Basic USB card.
The secret is the –b 57600 which tells avrdude how to
set the FTDI baud rate. Downloads pretty fast, too.
Q. I want to use simple radio control servos to run my robot. How fast do these servos go and can I use their own controllers to change their speed?
I like using only one controller line to control the
— Tom, Council Bluffs, IA
A. Tom, I’m assuming that you want to know how fast your robot will go when using a hobby servo and not how fast the servo runs. Those
two details are related, but
not the same. There are a
variety of hobby servos
available and they have a
variety of speeds and
power. Table 1 shows a
small selection of popular
hobby servos and a few
that are more expensive to
give you a quick range.
The speeds are given as
time, in seconds, to move
14 SERVO 03.2011