On Sat, 6 Jun 2009 08:24:37 +0800, you wrote:

>The spec looks ok for a low end PLC. The problem may be the software.
>What will be the programming language used for the user? Ladder is
>the basic requirement if you want to call it a PLC.

I said  "PLC like application for a PIC24". I am not trying to invent a
PLC. I have to time some inputs with at least 10us resolution and do some
real time calculation and response at about 1kHz. The system I am doing
this for already has a small  PLC. While adding some 24v I/O to communicate
with the PLC I realised it would simpler to add a few more and take over
the PLC function as well. 

>PIC24 can do the job. But the price of STM32 is similar to PIC24 and
>arguable more powerful or cheaper to develop (arm-gcc + openocd with
>cheap JTAG debugger).

I already know the PIC24 and am set up for development, for initially a one
off (+ spare) price of the chip was irrelevant. 

I looked for an off the shelf board with a PIC24 (or maybe dsPIC) and
didn't find anything that by the time I added the interfaces and enclosed
it looked cheaper and/or easier than designing a custom board and building
a couple. 

I am interested to know if anyone else has been in the same position of
needing a PIC24 development board for PLC like industrial control
applications and what other features they might consider useful. 


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