gnupic: blinking leds with usb port
Subject:
Re: blinking leds with usb port
From:
Byron Jeff ####@####.####
Date:
28 Feb 2013 14:15:18 -0000
Message-Id: <20130228141457.GA16943@mail.clayton.edu>
On Thu, Feb 28, 2013 at 08:33:13AM -0500, Maxime Larocque wrote:
> Hi Jorge,
>
> Le 2013-02-28 04:03, Jorge Barros de Abreu a écrit :
> >The goal is make the same project for usb port with small and low cost
> >eletronical circuit.
> >
> >If you know a link in the internet with a similar hardware project for usb
> >port i will apreciate if you put the link here.
> I don't have any link on hands; it depends on how you define low cost
> and the quantity you make to make.
>
> For fast personal projects, I like to use a USB-to-serial adapter and
> then connect a PIC with a serial port to it. It also allows for more
> complex or time-critical timing if the PIC controls the output (like a
> PWM, servo controller, etc). Also, there are a lot of examples out there
> to communicate through a serial port.
>
> Otherwise, you may have to use a chip with USB (PIC or other); I do not
> have any experience with this, but it may be more complex if you need to
> create a device driver specific to your device. Also, the packaging of
> the chip may not be convenient for a Do-It-Yourself-er. It could be a
> good option if you plan to produce a lot of your devices.
The problem with both of these options is the chicken and egg problem of
programming the PIC. It instantly stops being a low cost, low hassle
project if you have to order and purchase a programmer. One of my long
standing projects has been low cost easy to build "code dumpers" that could
be used to drop a bootloader onto a self programmable PIC. Then the
bootloaded PIC can be used with an appropriate interface for continued
programming. The parallel port was the best port for this type of activity.
Sadly it, and serial ports (with the exception of USB to serial), a rarely
available in modern machines.
I've made quite a bit of progress since my last foray into this discussion.
I have a working bootloader that uses a simple two pin bitbanged serial
interface that is stable enough to be released. The host software is
written in Python and runs on both Linux and Windows machines. Macs will
work with FTDI USB/serial adapters I think.
I have a preliminary code dumper written in Python that I've had some
limited success with. It uses a USB/Serial adapter and some voltage clamps
to program 16F1XXX parts. It's not stable enough for release yet.
Once finished, the combo facilitates bootstrapping a working PIC
development system using only a reusable $10 USD USB/Serial adapter and a handful of
discrete components available from the local electronics shop (or your
local junk box of parts).
BTW If you decide to go the USB PIC route, then from a programming
standpoint the easiest way to get started is to use the JAL USB library. A
virtual serial interface can be created in about a dozen lines of code.
Here is a tutorial showing an example project using a 18F14K50 USB chip.
http://jallib.blogspot.com/2009/07/pic-18f14k50-usb-interface-board-part-2.html
Hope this helps,
BAJ
>
> The third option would be to buy a USB to TTL output device; I do not
> know the price of such things. You may even consider a Raspberry Pi in
> this case; even if it is a bit overkill (I am not sure if it can work as
> a USB device). The price may actually be lower than simple USB-to-TTL
> devices.
>
> Regards,
>
> Maxime
>
>
>
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--
Byron A. Jeff
Chair: Department of Computer Science and Information Technology
College of Information and Mathematical Sciences
Clayton State University
http://faculty.clayton.edu/bjeff
