I would like to use the Pololu USB-serial adapter (version 1.0) as a serial programmer for Arduino boards, which have a capacitor connected between the microprocessor reset line and DTR of the serial port (TTL levels). The programmers I’ve seen use the FTDI USB adapter.
Does the Pololu USB-serial adapter (which uses the CP2102 chip) and Windows driver support a low pulse on the DTR line? Or might *RST perform this function? Has anyone used this adapter to program an Arduino board?
You should definitely be able to use the Pololu (or any CP2102-based) USB to Serial adapter as an Arduino programmer, right from the Arduino sketching environment (I’ve done this once before when I was messing around with adapting the Arduino bootloader to run on an Orangutan). The DTR pin on the adapter is normally high, and the Arduino environment will assert DTR, bringing the DTR pin low, to reset the board before programming.
One thing to keep in mind is that high for a CP2102 is 3.3V, so if you’re using a 5V Arduino you should probably throw in a current-limiting resistor.
Indeed, the Pololu USB-serial adapter works perfectly as an Arduino board programmer. I wired the adapter as recommended for the FTDI chip and wrote a batch file that executes the Arduino version of avrdude. I’ve read that only certain later versions of Arduino avrdude support toggling the DTR line as *RESET.
I reassigned the Pololu serial port driver to be COM1 (My Computer > properties > hardware > Device Manager > Pololu USB-serial> properties > port settings > advanced), and executed flash.bat from the command line to program.
flash.bat contains the single line:
C:\arduino\hardware\tools\avr\bin\avrdude -p atmega328p -P COM1 -c stk500v1 -b 57600 -CC:\arduino\hardware\tools\avr\etc\avrdude.conf -U flash:w:main.hex
It is probably possible to build this command into WinAVR, but I haven’t researched it. The WinAVR version of avrdude may not work, as it supposedly does not know about toggling DTR.
BTW I’m working with the SparkFun Openlog data logger, which is fun to play with. Presently it only logs TTL-RS232 data. If it had more I/O lines, at $24.95 it would be extremely interesting.