Propeller Serial Programming schematic

Forrest

I noticed the Propeller serial programming circuit has gone thru at least 3 revisions that I'm aware of. The first had (3) transistors and (10) resistors, the schematic posted in the Propeller Schematics area has (3) transistors, (7) resistors and (1) capacitor and the one posted in the Propeller DataSheet 0.2 has (3) transistors, (4) resistors and (1) capacitor.

Has the one in the DataSheet been verified? If so, I think Parallax should update the schematic posted on the Propeller Diagrams, Schematics and Images area to be consistant.

Beau Schwabe

Forrest,

The original release (3t / 7r / 1c) located in the Propeller Schematics section, is the one that I came up with.
The one posted in the Propeller DataSheet ( http://www.parallax.com/propeller/media.asp ) is a simplified version of the original.
I agree that the version in the Schematics section should match the one in the DataSheet section.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Paul Baker

The pdf in the Propeller Diagrams and Schematics will be updated, thanks for letting us know about the discrepancy.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Propability

I'm getting ready to make the rs232 adaptor with a usb to rs232 cable(finally got a laptop, no rs232 port). I was going to make a little jumper on the proto board to get the 3.3 volts for the circuit and I was wondering if there is a way to get that from the usb rs232 cable ( which works with the ftdi drivers ok on the laptop(Vista)to talk to ·another system that uses rs232 for comms ).

Pete

tekochip

Is it possible to revise the reference circuit to be a little more robust from noise, a lower Z or a little filtering? The Reset line is far too sensitive and is easily tripped by static electricity. Right now I short the base of the transistor whenever I'm not using the interface because it will literaly trip if somebody walks by my desk while dragging their feet on the carpet.

Paul Baker

Tekochip, what you are experiencing is resultant of the fact DTR is capacitively coupled, but this is required to make sure all terminal programs work correctly since some will just assert/deassert the line and not pulse the line as is expected by the Propeller. It may very well be a ground loop issue, in which case you can try to rectify this by placing opto-isolators on your 3 signal lines and isolate the ground of your Propeller from your computer.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.