Stamp Resets When Connecting PC

John Burrow

All,

My Basic code·is not yet stable, so there are times when I want to plug in my·laptop to use HyperTerminal to look at·Debug messages.

The Stamp is·connected to my laptop's USB port·via the Parallax USB to Serial adaptor

As my laptop powers up, it causes the·Stamp goes through a couple of resets. The resets·happen·during the PC power up before I open HyperTerminal. They also happen·when I open HyperTerminal, or the·Stamp Editor.

The same behaviour is exhibited by a BS2 and two·BS2P's. All 3 are mounted on carrier boards and powered by Radio Shack 9v 1000ma wall wart.

Can anyone tell me why I get the resets?

Thanks, John Burrow

Mike Green

During the PC power up and while the USB drivers are figuring out what's connected and initializing the USB devices or when the serial port is opened (and closed), the DTR line may get changed. This is hooked up to the Stamp's reset line via a couple of capacitors which turn a transition on the DTR line into a reset. This is a normal part of the download / identification process, but a side effect is these resets.

Phil Pilgrim (PhiPi)

The BASIC Stamp will reset when there's an edge on the DTR line (RS232, pin 4). This can occur when powering up your PC, starting HyperTerminal, or just connecting your RS232 cable. To keep this from happening, you can rig up a special, intermediate RS232 cable to plug into the DB9 end of your USB to serial adapter with pin 4 clipped out of the male end, which will keep the reset pulse from reaching the Stamp. You won't be able to program the Stamp with the hacked cable in place, though, since doing so relies on the DTR signal.

-Phil

Post Edited (Phil Pilgrim (PhiPi)) : 1/9/2008 12:11:03 AM GMT