View Full Version : UM232R USB-serial adapter

01-06-2009, 05:49 PM

I'm wanting to get started in Propeller development, and I'm putting together a list of what I need to get.
I have a UM232R USB-Serial development module and I wondered if anyone has used this for programming a Propeller, instead of a prop-clip or similar?



01-06-2009, 06:28 PM
hello Anton,

I don't know this type. If it is a simple USB2RS232-converter it should work.

I used a usb2rs323conv. from digitus. On my PC it worked well. on my laptop unreliable.
the main chip of the digitus is from manufacturere prolific

Converters with a FTDI-chip seem to work much better. (the parallax-converters use them too.

To connect directly to a propeller you need a voltage-levelshifter. standard RS232 is +12V/-12V
For example the MAX2323 which is for supplying with 3V and signals of 3V on the propellerside
can do the levelshifting from +12V/-12V to 0V/3.3V

for a superminimum start you just need a proppellerchip, 5MHz chrystal, 32kB EEPROM RS232 interface
that's all

best regards


01-06-2009, 06:40 PM

I'ts a USB-serial UART interface with configurable 1.8-5v logic output, mad by FTDI.


With what you say, then it looks like it should work OK.


01-07-2009, 02:58 AM
This module should work fine, if you add a little circuit at the DTR Pin to produce a correct Propeller Reset (schematic attached).
It's also important that you set the module to 3.3V output level (not 5V).


01-07-2009, 03:01 PM
Hello Ariba,

thank you very much for adding this info ! VERY important !

Without the reset circuit communciation would not work at all

best regards


01-08-2009, 04:43 AM
Hello ascoetzee:

I made a prop clip compatible module with this same FTDI module some time ago in a protoboard.

The PDF attached is my schematic of the connections between the module and the Prop. It generates the reset signal using DTR# pin, a transistor and one resistor as Arriba wrote. Also it have two fancy leds for in & out data transmission between PC and prop. http://forums.parallax.com/images/smilies/turn.gif

To make the leds and DTR# signal to work, you have to program the FTDI chip using the MPROG utility program (from FTDI web site) taking care to not using the D2XX driver http://forums.parallax.com/images/smilies/nono.gif , because it didn't work with the Propeller tool or Prop Terminal.
Also you can change the windows descriptor of the module that shows when you connect to PC.
In the attached image you can see my configuration.

Be lucky!

Gatuno. http://forums.parallax.com/images/smilies/tongue.gif

01-08-2009, 06:06 AM
Gatuno (and Anton)

if you use MPROG anyway, you can also invert the DTR output signal, and spare the Transistor circuit.
Then only a Captacitor is needed:

DTR ────────── Res Prop

I think it works also without the capacitor, if you only use PST and PropTool. But most other serial Terminals have the DTR in wrong state, and the 10nF lets then only the transitions at DTR pass to the Reset input.