🚀 go-pugleaf

In article <29569@castle.ed.ac.uk> wbg@festival.ed.ac.uk (W Geake) writes:
>In order to run an analogue to digital convertor module from a serial
>port, I want to send a byte from the port every 10 ms.  This sets the
>sampling rate, so the accuracy of the interval is very important.  The
>VB Programmer's Guide mentions BUILT IN POTENTIAL FOR ERROR in timer
>controls, a great euphemism if ever I heard one.  Can I get good precision
>from VB, or do I need to work in C (please not!) or C++(worse still) or
>write a VxD (I'd rather sell life insurance)?

Bill, you have a fairly hairy problem on your hands.  In order to get that
rate, you are going to have to grab one of the timers (probably the keyboard
scan timer) and reprogram it to 100 Hz.  Then you are going to have to install
a custom interrupt handler to pump the serial port.  And you STILL have to
worry about DOS or something else taking over your machine for many milliseconds
while it does something it thinks is more important.

If I were in your shoes, I would grab a microcontroller or a single-chip
microcomputer and dedicate it to pumping the ADC.  If all you need is a pulse,
just so the ADC module gets SOMETHING, then something like a Motorola 68HC705K1
would probably work just fine.  If you need a real-live character, then an 8751
or something along those lines (68HC11, say) would work well.  (Note: I am
extremely fond of the New Micros Inc. F68HC11: it comes with Forth blown into
the on-board ROM.)