RS-232 communication and event counter

[abionnnn]

event counter +avr

I've got a big task to complete by a month when my thesis is due. I need a bit of advice, so that this doesn't take longer than neccesary.

I've got two inputs, a frequency standard 5MHz sine signal which I'm going to use as a time stamp by sending it to a counter/divider IC. This signal would then have to go to a microcontroller which can be polled via RS-232 which then would send a binary string of a counter representing the time in milliseconds.

At the same time that this is happening, a rotating table with LEDs fitted on which would send pulses at a non-periodic rate. I need to input capture these pulses and increment a counter which would represent the table's position. We've set up one of the pulses to be a doublet which would kind of be a failsafe incase we miss a point. When a computer polls the microprocessor for the time, we would also like to send a string representing the position of the table.

Obviously, we're going to need a fast microcontroller to handle things like this reliably. Can anyone suggest a microcontroller that is up to it? More importantly, a ready made board with it on it which can be delivered to Australia within a week or so?

Thank you all for your time.

 

[Mr_Programmer]

counter ic poll increment

1. question:
Your time stamp / milliseconds counter how many bytes do you want to use ??? I mean, if you only want to extract milliseconds... well, not the biggest problem. I would suggest a µ-controller with a 16bit wide capture / compare unit. Or even better use the 5MHz to clock the µ-controller!

2. question:
You want to detect the position of your table? In both directions?? I mean you turn left and then right, and after that you have to know the direction...???
If so you need at least 2 LED's, that will be activated not at the same time.
With which speed you will turn the table?
I think you can use simple interrupt inputs to detect the position, as long as you don't want to detect thousands of rpm's.

So my suggestion, use Texas Instruments MSP430 µ-processor for this, MSP430F1222 or MSP430F1232, they have also a onboard UART, so you don't need to poll. The delivery should be easy buy a FET-Tool from TI, with this you will get a JTAG programmer, a 4kb C-Compiler trial, a board with ZIF-socket and 2 processor samples. On the board you have access to all IO's, thats it. You can also take a PIC or a AVR, I think the speed will be no problem.

 

[abionnnn]

event counter microcontroller

Dear Mr_Programmer,

Thank you for your reply,

>Your time stamp / milliseconds counter how many bytes do you want to use ??? I mean, if you only want to extract milliseconds... well, not the biggest problem. I would suggest a µ-controller with a 16bit wide capture / compare unit. Or even better use the 5MHz to clock the µ-controller!

The thing is, we want to extract milliseconds, but we also need the rest of the time (hr, min, sec), so we'll probably store it in say 4 bytes. Each run of our experiment will be roughly 4 days. For some reason I don't trust the microcontroller to do the capture/compare ... I don't know why, discrete logic is always more reassuring to use... :wink: (e.g. a 4060)

>You want to detect the position of your table? In both directions?? I mean you turn left and then right, and after that you have to know the direction...???

Well, the table will only be rotating in one direction at a certian frequency, but this frequency will be a LOT (by almost 10 orders of mangnitude...) less stable than the best frequency standard that we are using, and the stepper motor itself is likely to miss steps. That's why we have a failsafe IR emitting diode, and a detector externally which is connected to a 555 timer that gives us a pulse whenever one of them are detected.

>With which speed you will turn the table?
I think you can use simple interrupt inputs to detect the position, as long as you don't want to detect thousands of rpm's.

We're going at 3rpm-6rpm (probably the latter for most of the parts of the experiemnt that I will take part of).

The Ti Microprocessor you mention sounds familiar, but I'll probably have a hard time tracking down a supplier in Western Australia.

Thanks!