mckenney@talos.pm.com (Frank McKenney) (04/13/90)
I am attempting to interface a dollar-bill acceptor to an IBM PC-
type computer. The device is controlled via three 4N37 opto-
isolators set up for +5V operation, and generates three relay
closures and a single +5V TTL signal as outputs.
My problem: can I use a "standard" LPTx printer port to interface
with this device? If I can, then I can use a cheap ($20-30) LPTx
card. If not, I'll have to go with a more expensive ($165-$200)
TTL Parallel I/O card. This is a significant difference in cost.
The TTL device output should not be a problem, and I can do
software debouncing on the relay closures. What I don't know is
whether the 74LS374 output signals (the LPTx DATA0-7 output
signals on pins 2-9) are strong enough to drive the LEDs in the
4N37 opto-isolators.
Does anyone have any experience using an IBM-type Printer Port to
drive something requiring more than a single TTL "load"?
Frank McKenney
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