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USB IO PICs or similiar

  1. Apr 23, 2012 #1
    Hey all,
    I'd like to apologise in advance if my post/question seems overly ignorant in any way, also this is sort of an "Hello Forum" and questions combined. I've not used a forum before for help with electronic projects :) I've been looking at basic relay/switching control from a computer so that eventually I can build up to using it in conjunction with RC circuits or what not to do all sorts of fun things. However the most material I've come across is C++ interfacing with the old serial ports.

    I have a fair working understanding of both C++ & Electronic design but I won't claim to be anywhere near knowledgeable on either, I'm still studying engineering at college...

    Anyway, on to my question. Is there any material related to using USB PICs as simple IO devices? I don't really want to seem to be asking for a hand out, just interested if there is any reading material available? As I'll gladly get my head in a book. I have no idea where to begin with regards to programming a PIC, especially with USB interfacing, since it's all ASM as I understand? Just wondered if anyone had any advice on where I should go with this?

    Cheers in advance for any info you can provide and also, sorry for the quality of this first post :)
  2. jcsd
  3. Apr 24, 2012 #2
  4. Apr 25, 2012 #3


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  5. Apr 25, 2012 #4
    I used to design controller with USB interface. I used micro controllers from Cypress. At the time, they had a whole family of chips based on Intel 8051 micro controller. Go on their website and see what they have today.

    BTW, I don't think you can use solderless breadboard for USB like the picture in one of the link. USB II is 400MHz!!!! You have to have balance differential 90ohm lines for that. USB is RF in every sense. Those plug in wire bread board is no good for any significant frequency.
  6. Apr 26, 2012 #5


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    You can probably do low speed USB (<1.5 Mbps) on a breadboard without too much difficulty, but anything higher would probably be difficult.

    For quick and dirty (and reusable) USB, you can get FTDI's UM232R (about $25 from most vendors):

    They're based around the FTDI FT232R family of chips (virtual com port and lower-level drivers are available for Windows, Mac, and Linux), which are the same ones used in most of the good USB-RS232 adapters (which also use the aforementioned drivers). Pretty good throughput (supposedly up to 3+ Mbps) and you can use standard UART handling and programming (on both the PC and micro side).

    There's also an emulated (but low-speed, i.e. 1.5 Mbps) USB firmware for the Atmel AVR--V-USB. I don't know much about it, but I believe it's the same one used in more recent variants of some Arduinos (I believe older ones used the aforementioned FTDI).

    Not super fast, but good enough for hobbyist use in an era where serial ports are going extinct.
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