View Full Version : rs232 propeller reset

12-29-2009, 10:09 AM
I have my demoboard connectd to the serial port of my pc, the pc running visualbasic. When the visual basic program closes the comm port, the propeller does a reset. How do I prevent this?

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Peter Jakacki
12-29-2009, 10:46 AM
disconnect the DTR signal for normal operation as this is used for reset control.


12-29-2009, 03:29 PM
If you disconnect DTR, you will need to reconnect it once again to program the propeller. You may also try changing the serial port connection to the propeller from DTR to RTS. As it is now, the Propeller Tool V1.2.6 (current) pulls both DTR and RTS low when it programs the propeller. But it may be that your VB application won't pull RTS down when it terminates, you'll have to try it out and see.

You can control which pin does the propeller reset, RTS, DTR or both in the propeller tool via Edit > Preferences > Operation > Port Management > Propeller Reset Signal. However I have found this setting to be dysfunctional, the propeller tool always pulls down both RTS and DTR no matter how you set this option. Parallax has refused to even reply to my email and forum postings regarding this bug.

Regards, David

Toby Seckshund
12-29-2009, 05:07 PM
I have put a jumper on my inteface to prevent this. I also put two on to be able to swap rx and tx over ( having got it wrong before,and of course, never since)

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12-29-2009, 07:28 PM
Did you verify my conclusion that the propeller tool V1.2.6 is pulling RTS down with DTR no matter how you set it in Preferences. More feedback would help us if you verify this. In-general (may not help your specific situation with your VB app), if the propeller-tool leaves RTS alone (high) when programming then we can make a serial dongle that is pin-compatible with the very expensive USB prop-plug, no power needed from the target propeller board (all parallax boards off-the-shelf) - hence the requirement for another pin. As this issue goes on and on without parallax response, it seems either parallax is too busy to deal with this bug (likely) or they are intentionally pulling both DTR and RTS low no matter what to make prevent the creation of inexpensive serial cables that would take market-share away from the prop-plug (unlikely IMHO knowing Parallax). But soooo long without a response from parallax worries me.

Regards, DR