help with transistors as switches

[MikeMl]

I have done lots of data acquisition and data streaming using PCs. The solution to the real-time problem is to equip the interface with a FIFO memory with sufficient depth to bridge across the periods when the PC goes to sleep. A lot of the commercial data IN/OUT cards (A-D/D-A) use this technique.

It is very difficult to do this through just a Parallel Port.

 

[frubo]

I was thinking something similar but I dont necessarily have to stream it if that would be easier. Lets say that I have a data file where there are a series of pairs of numbers(both could be 8 bit). The first number indicates which switches should be on/off and the second number indicates the delay in ms until the next change in the switches . This is what I was trying to do in real time with my program using a simple loop.

So here is my new idea. First I would load the entire data file into some memory on my circuit. Once it is loaded I would have a switch that starts the whole sequence. I would have 2 8-bit registers, one register would hold the pattern for the switches and the other one would have the delay(ms). Then I would also have a timer with a 1khz frequency which outputs to a counter. Once the counter reaches the number in the delay it would reset and both registers would load the next byte respectively and repeat the process.

It seems simple enough for me to do but I am unsure about what specific parts to buy, especially the memory. I was also considering switching to usb instead of parallel but still keeping the same basic idea.

 

[MikeMl]

When controlling fixed-paced processes with a PC, I have used a µcontroller like a PIC or TI 430 to control the timing of the process, and then just have the PC send or receive the control parameters and/or data asynchronously to the µcontroller using either the PC's serial-port or parallel-port. This is a type of software FIFO. You have to use µcontrollers that have sufficient RAM.