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HP82164A USB upgrade

Posted by Hans Brueggemann on 18 Sept 2010, 10:09 a.m.

the HP82164A HP-IL/RS-232 interface is still one of the more common ways (besides J-F Garnier's PILBOX) to connect HP calculators with HP-IL capability to a PC or a laptop. unfortunately, COM ports on those machines of newer production dates have almost ceased to exist, and this manko is today euphemistically called "legacy free".
i wondered whether it would be feasable to modify an HP82164A into an RS-232 over USB interface, and yes, it can be done easily, thanks to J-F's inspiring work on the PILBOX interface.
here goes:
what you require is an FTDI UB232R USB Mini-B FT232R Evaluation Module, an HP82164A interface and, of course, some soldering skills.

1) open the HP82164 by removing the three screws at the bottom of its case.
2) inside, find the 6551 ACIA chip. it is the 28-pin chip that is positioned closest to the DB-25 serial connector.
3) connect the USB module to the ACIA with a 6-wire ribbon cable as follows:
ACIA pin# USB module connector pin#
1 (GND)----------J1-1 (0V power pin)
8 (RTS#)---------J1-3 (FT232R RTS pin)
9 (CTS#)---------J1-4 (FT232R CTS pin)
10(TXD)----------J2-2 (FT232R RXD pin)
12(RXD)----------J2-1 (FT232R TXD pin)
15(Vcc)----------J1-2 (+5V power from USB interface)

lay the ribbon cable sideways through one of the small wall slots of the 82164 interface housing and re-assemble it. a small piece of shrink tubing over the USB module gives some protection, and there you have it:
a fully HP-IL-spec-compliant RS-232 over USB interface. and yes, it is bus-powered, it draws exactly 100 mA from the USB interface. no need for a 82066 wall brick.
now, install the FTDI drivers, hook up your system and have fun!
hans brueggemann, sept. 2010
edited feb. 2013 for additional RTS/CTS connections.

Edited: 28 Feb 2013, 6:34 a.m.

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