in the past I had tried to implement the RS-232 interface to my Challenger 1P by following the instructions in "The first book of Ohio Scientifc Vol. I" and in the Professor Mark Csele: Ohio Scientific Computers web page. Unfortunately I never was able to make it work, and I abandoned the project. I then fell back to loading WAV files for BASIC programs and cc65-compiled programs over the headphone port of my laptop.
The implementation of the RS-232 interface required to scratch out a pcb track on the bottom of the C1P board, and the addition of switch to toggle between RS-232 and cassette operation. At some point in time I decided to remove the RS-232 connector and the switch, as it was useless anyway. When I yesterday tried again to load a program over the cassette port, it didn't work, and I was completely stumped first, because previously it had worked very reliably. Only after re-reading the instructions for the RS-232 implementation in the book and in the corresponding section in the Professor Mark Csele: Ohio Scientific Computers web page it occurred to me that I had to add back a jumper to make the cassette port work again.
And here I got confused. On Mark Csele's web page it says this:
However in "The first book of Ohio Scientifc Vol. I" on page 80 it says this about installing the switch:The actual 'W10' jumper which must be cut is located on the bottom side of the board and detailed in the photograph. With this jumper removed, even cassette operation requires a jumper on J3.
Connector J3 Wiring (for Cassette Tape operation):
Jumper J3 Pin 5 to J3 Pin 6
Connector J3 Wiring (for RS-232 operation):
Jumper J3 Pin 4 to J3 Pin 6
J3 Pin 2 (RS-232 Out) to DB-9 Pin 2 (Transmit to PC)
J3 Pin 3 (RS-232 In) to DB-9 Pin 3 (Receive from PC)
Board Ground to DB-9 Pin 5 (Ground)
Note that Mark Csele's instructions tell to connect pin 6 to either pin 5 or pin 4 for toggling between cassette and RS-232, while the installation of the switch according to the book will connect pin 4 to either pin 5 or pin 6 for toggling.Code: Select all
CONNECTOR AND SWITCH FABRICATION The first six pins on the molex connector, part #P2, are to be connected as follows: PIN # To location ... 4 Pole of SPDT switch, part # S1 ... 5 Out 1 of SPDT switch, part # S1 6 Out 2 of SPDT switch, part # S1
My own experiments seem to confirm that connecting pin 4 to pin 5 is the correct thing to do to enable cassette operation.
Can someone confirm or rebut that the instructions in the book are correct? I the book is correct, would contact Mark then for a correction of his instructions.
Thanks
Stephan