pete%slack.uucp@cs.utah.edu (Pete Ashdown) (03/13/90)
Rick Sterling was kind enough to post the pin-outs for the 48's serial connector recently. However, he did not specify what was needed to actually make the connector. Does anyone know the TRaSh-Shack equivalent to plug into that hole? Also, which pin is #1? "People should be beat up for stating their beliefs." - They Might Be Giants This is to certify and promulgate American Family Publisher's intent to award TWENTY MILLION DOLLARS to PETE ASHDOWN! Yippee! UseNet is on me everyone! [pete@slack.uucp] [...utah-cs!i-core!slack!pete] [slack=AMIGA!!]
madler@tybalt.caltech.edu (Mark Adler) (03/13/90)
There is nothing in Radio Shack that fits in the HP-48SX's serial port. The connector pins are either 2 mm or 5/64ths of an inch spacing, not the usual 1/10 inch (2.54 mm) IC pin spacing that Radio Shack DOES have an inline connector strip for. The error is too great to force such a connector on (I tried). I am currently jury rigging something up now. I found out (not thinking to call HP) that with the calculator facing up (the normal position), the first pin on the left is the signal ground, the second pin is receive data, and the third pin is transmit data (i.e. those last two are signals going into the calculator and coming out of the calculator, respectively). Pay attention to the serial connector on your computer, since there are two ways to wire it. Check which of pins 2 and 3 are in and out relative to your computer and connect the computer's in to the calcuator's out, and vice-versa. Just by the way, the RS-232 of the HP-48SX doesn't quite meet the RS-232 standard specifications. A "mark" is supposed to be between 5 and 25 volts, but the calculator only puts out about 4.1 volts for the signal. It would have required some extra hardware for the calculator to do otherwise, since it runs off of 4.5v worth of batteries. However, the RS-232 standard also specifies that the receiver should be able to detect signals in the range of 3 to 25 volts, so if the cable isn't too long, there should be no problem. And for the guy who wants an interrupt driven terminal program for the 48, that shouldn't be necessary. It already uses interrupts to maintain the buffer used by BUFLEN and SRECV, so all you really need is a machine language program that is fast enough to empty that buffer faster than it fills. Mark Adler madler@hamlet.caltech.edu
prestonb@hpcvra.CV.HP.COM (Preston Brown) (03/14/90)
>Just by the way, the RS-232 of the HP-48SX doesn't quite meet the RS-232 >standard specifications. A "mark" is supposed to be between 5 and 25 volts, >but the calculator only puts out about 4.1 volts for the signal. It would >have required some extra hardware for the calculator to do otherwise, since >it runs off of 4.5v worth of batteries. However, the RS-232 standard also >specifies that the receiver should be able to detect signals in the range >of 3 to 25 volts, so if the cable isn't too long, there should be no >problem. The I/O is specified to output a minimum of +/-3V into a 3K ohm load. This voltage is regulated and is not straight from the batteries. Very few users would want to run the serial port over long distances and using +/- 3V increases the battery life. Actually, the signal ground "SGND" is the system VDD. Preston