Chris... Thanks so much!  Great stuff... I can't believe that this material never existed before!  It has helped me (and I am sure others) out greatly!

In terms of programming the OEM Stamp-Lite, Chris indicated that "You can use one of the many RS-232 programming adapters I have seen which would include all the circuitry missing from the original schematic."  I really don't want to be a pain, but I am having an awful time finding a simple schematic of what one of these RS-232 programming adapters would look like.  I have seen several of them, but they all seem to work a bit differently.

HVW Technologies RS-232 Driver Module

http://www.hvwtech.com/products_view.asp?CatID=163&SubCatID=197&SubSubCatID=198&ProductID=289

Kronos Robotics Easy RS232 Interface Kit

http://www.kronosrobotics.com/xcart/customer/product.php?productid=16167&cat=291&page=1

Acroname Serial Interface Connector

http://www.acroname.com/robotics/parts/S13-SERIAL-INT-CONN.html

Pololu Deluxe Serial Adapter Kit

http://www.pololu.com/products/pololu/0126/

AWC RS-I Serial Interface Adapter

http://www.awce.com/rs1.htm

How would I know if any of these would work?  Would they work as a "direct connect" our would I still need the 4.7k resistor between Rx and TX?  Would I still need the 1N914 diode on the RX line?  Are these components only needed because of the USM2SER?

 Does anyone have a complete schematic (most likely based on a MAX232 or MAX233E) of how to build one that would be able to program the OEM Stamp-Lite?

Post Edited (Steve Joblin) : 1/26/2006 4:01:02 PM GMT

Steve,

   What might be better to do is compare the original schematic to the two LITE schematics.  Don't focus on the USB version, those changes are for the USB2SER only at this point.  Any RS-232 circuit you connect to either LITE circuit should be the equivalent of the parts removed from the original circuit.

   One thing to bear in mind is that the S_OUT line is driven HIGH, not floating and pulled HIGH as the S_IN line is.  What this means is that your circuit should expect that S_OUT is driven.  I hope this helps.

Steve,

   Yes, I do have one...The original schematic for a BS2 OEM is linked above.  That schematic shows all the "extra" parts I removed from the schematic to create a LITE version.  You could effectively make a programming dongle for RS-232 using that part of the schematic.  You would just include those parts and then you could plug it in to the LITE schematic (into the S_IN and S_OUT pins).

Hello everyone,

   I know the question has come up before about how to connect directly to the interpreter through the serial port using a MAX232 (or similar) Line Driver and there were no previously published articles that I was aware of.  As of today one of our customers has used the schematics in this thread as a guide to perfect this and connect directly to the BS2p40 interpreter chip (SX48).  The following schematic he came up with and wanted to share it with anyone else trying to connect in this manner.  From the customer:

Chris,

I came up with this design, modified my board and it is successful.  If you want to add this to your zip files I am forwarding this along.  I have been testing code and using the PBasic Stamp Debugger without any issues.  I appreciated your help and therefore am sending this to help others. 

George Calvas (Ford Motor Co.)

   Bear in mind that the BASIC Stamp requires echo on the RX/TX lines for the Editor to recognize the BASIC Stamp.  In this manner the diode is required due to assertion of the other line across the 4.7K resistor.  George has successfully married this theory on the RS-232 side of the MAX232.  He hopes this helps someone else.  Take care everyone!

---

Chris Savage

Parallax Tech Support

 

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