--- In Electronics_101@..., John Woolsey <jwoolsey@...> wrote:
I am working on my project. Although I want to make a USB I/O device, I
have realized I just don't have the confidence for it. So I have decided
to buy a USB I/O device and get on with things. I will come back to this
later once I am done more of the project.
So I am trying to find Criteria for the USB device. At the current time
my list is:
Must have Linux drivers (accessible from Java).
Must have Pulse Width Modulation (probably two per device).
Reversible ports would be good Input or output on each pin.
Should have at least 16 ports.
It would be nice if you could time ports to flip on for a short period
(to not burn out solenoids).
It would be used for:
Turning on and off lights. (I think 9V bulbs. Might be 12V).
Sense switches closing.
Firing Solenoids at 48V for short periods so they don't burn out
Holding Solenoids via PWM to keep them fired but not burn them out.
For 48V I am looking to get a power supply and then use a power transistor.
I have looked over the internet and I have found tons of boards that
fit. But I have no experience on which one to choose or what is the
"best board". I am in Toronto ON Can so if there is a supplier there
that would be great.
So advice me please. Any suggestions would be helpful.
thanks
John
I might approach this in one of two ways: First, I would grab up a microcontroller that has the hardware I/O, timer and PWM gadgets you require. To this I would add an FTDI USB->RS232 chip so that I was certain that drivers were available for the chip. Your host application can be written in any language that can talk to /dev/ttyUSBx. The USB chip will show up as a VCOM port under Windows.
The second approach would be to use a chip that can already handle USB and still had all the I/O, timer and PWM gadgets. The NXP LPC2148 comes to mind as it has a USB device gadget and code is available to make it look like a serial port: www.jcwren.com/arm There are many Microchip PICs that also meet these requirements.
Both of those approaches take a ton of development time. Maybe the Arduino is a better platform. It certainly works on all the Windows platforms and it also works on Linux. Again, there is an on-board USB serial chip so your application program just needs to interact with a serial port. Send commands, retrieve results; make up a language for interaction and you are good to go.
I have been playing with the Arduino all morning so, naturally, it comes to mind as a very nice platform for this kind of thing.
Richard
