[i_am_fubar]

This will be, depending on its success. The first of many products in a range I have in mind. Including a computer based oscilloscope, power supply, wireless Data links, analogue sig-gen... etc.

Membrane keypads are nice, have started using them at work. but theres a £300 set up charge ($600ish)

Output was going to be only 5v TTL for direct connection to logic.

Next question, for a few extra dollars, would it be worth having a back lit LCD display as opposed to a reflective one?

Also, out of the following list, which would be most desirable?:

• Digital signal generator
• RS232 analyzer and generator
• Analogue signal generator
• Computer based oscilloscope/spectrum analyzer
• Computer controlled analogue and digital I/O interface box (with C libraries)
• Universal motor driver (stepper, DC, servo) computer connection.
• Pulse timer/Chronograph

[mechatronicsman]

Output was going to be only 5v TTL for direct connection to logic.[/LIST]

Trust me.. with that limitation you will loose 70-90% of potential customers.

5 V levels are phasing out quickly. Less and less embedded electronics/MCUs support that now. 5 volt is mostly used in industrial control and white goods appliances today.

And TTL 5V levels are definitely useless in most applications. A TTL level only guarantees 2V out on logic high. And a CMOS integrated circuit (most ICs today are CMOS) need 70% of VCC for detection as high. I.e. CMOS high level need to be at least 3,5V to be guaranteed to be detected as high. So if 5V only be sure the drivers are rail to rail drivers, not TTL drivers.

This is one of the reasons many people struggle driving circuits directly from the parallell port of a PC, as old PCs have TTL signal levels, not suitable for directly interfacing modern CMOS stepper drivers for instance.

So to be usable to other applications than CNC and industrial control applications you need at least to support 3,3V levels in addition to 5V. Preferably adjustable amplitude between 1,8 to 5V.

-bjorn

[i_am_fubar]

I didn't realize all that. Thanks for the info dump.

I did mean full rail to rail 0v,5v outputs. Wasn't aware that TTL was so grey.

I guess it wouldn't be difficult to add a variable amp at the output to give 0.5v - 8.5v.

I think I may need a bigger box.

Sam.