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View Full Version : Question about using USB2SER to talk to BSII via debug terminal



kogerat
05-20-2006, 11:48 AM
I'm trying to use a USB2SER to communiate with a BSII over the serial com port. I'm using windows XP and have installed the driver and reduced the latency setting to 1 per the installation instructions. The comm port is set to 9600 baud, 8N1, no flow control.·On the debug screen, the key strokes are echoed back to· the screen and the RX and TX led toggle on the USB2SER, so it looks like the USB2SER is·talking to·the PC, but I seem to be getting any I/O from the BSII. The USB2SER is wired to a male DB9 connector, VSS to pin 5 of the DB9, TX to pin 2 of the DB9, RX to pin 3 of the DB9 and RES to pin 4 of the DB9. The eventual goal after I learn how to get the USB2SER to work with a BSII is to use the USB2SER to·replace the RS232 serial port on a Motorola HC11 trainer for a project at school. I'm using a BSII·example program DEBUGIN DEBUGOUT·program that I have attached. Any help or guidence I can get is immensely appreciated.

Jim K

Chris Savage
05-20-2006, 12:21 PM
Hello,

·· The USB2SER is not designed for this purpose.· The USB2SER communicates using TTL level serial, whereas the BASIC Stamp is expecting inverted RS-232 level signals.· If you had an OEM BS2 you could talk to it by bypassing the serial interface circuitry as shown in the Projects Forum.· You will either need to use a MAX232 or similar RS-232 level driver or get the actual FTDI USB to Serial Adapter we carry.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

kogerat
05-20-2006, 12:59 PM
Thanks for your reply Chris. I have a PDB with a MAX232 and DB9 connector. Would it be·possible to set up some kind·of communication through that port?
Thanks again.
Jim K

kogerat
05-20-2006, 02:33 PM
OK,sometimes I'm a little slow. But , I get it now. I mistakenly assumed that the USB2SER also performed the same task as a MAX232 and output a +/- 10v RS232 signal. If I underestand right, it outputs a 0 to 5v·TTL signal. So, if I want to communiate with something that needs a RS232 level signal, I need to connect the output of the USB2SER to the 5v side of the MAX232 to get a RS232 level signal ouput from the MAX232. This also means that I can communiate with the BSII's I/O pins directly with the USB2SER using the SEROUT and SERIN commands does it not?

Thanks again Jim K

Chris Savage
05-21-2006, 05:01 AM
I think you have it now...But on the MAX232 you'd need to be able to get the DTR line over too.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)