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Anyone working on a USB slave stack? — Parallax Forums

Anyone working on a USB slave stack?

joeysr20detjoeysr20det Posts: 8
edited 2013-11-28 11:54 in Propeller 1
I've searched quite a bit and all I have come across is the USB Slave stack by Bradc. Has anyone else written a USB slave stack? I'm really in need of one. I've looked over Bradc's implementation, but it seems to be missing quite a bit. Is Parallax ever going to consider writing one? My past projects have been with Microchip PICs which have a built-in RTC, usb support, builtin eeprom, etc... I seem to keep hitting one hurdle after another with this Propeller. I love the coding environment and multi-cores, but seemingly too many short falls :(

Comments

  • MagIO2MagIO2 Posts: 2,243
    edited 2013-11-27 01:37
    Implementing the full USB specs is simply out of scope for the propeller. Too much and too fast, especially when we talk about USB 2.0/3.0.
    So, maybe parallax should spend some time for a nice library which allows to make good use of a FTDI device, just to tell possible customers "Hey, you can use USB this or that way with the propeller".

    The idea behind a propeller is to not have all those build in hardware (except of the video support), but either implement behaviour this hardware in a COG or attach some external hardware specialized to the task.
    For example: what is the benefit of having serial interface, i2c, adc in such a microcontroller when you don't make use of it in the project?
    what is the benefit of having a 12 bit ADC buildin, when you later on need a 16 bit ADC?
    And then show me the PIC or AVR which has 8 full duplex serial ports in hardware! (Even 16 serial ports are possible with the propeller)

    My impression when starting with the propeller was different. I liked how easy it was - without any knowledge of those tons of special registers you need to know for PIC&AVR programming - to attach a keyboard, a TV, a VGA monitor, a mouse, a serial interface, ......

    And in the end you as an engineer need to know the limits of the systems you like to use in any case, that's also true for PIC or AVR. Or would you try to use a PIC for real-time image processing?

    If you see too many hurdles, simply let the forum know what you want to do with the propeller and you'll get an honest opinion on weather the propeller fits or not.

    BTW ... welcome to the forum.
  • jmgjmg Posts: 15,173
    edited 2013-11-27 11:49
    joeysr20det wrote: »
    I've searched quite a bit and all I have come across is the USB Slave stack by Bradc. Has anyone else written a USB slave stack? I'm really in need of one.

    None I've seen 'fully functional' on the Prop.
    There is a 'somewhat' solution for AVR, that is low speed only, and outside the specs in some areas. so if you have lots of free time, look at porting that ?

    Keep in mind however, that USB solutions keep dropping in price, here are some quick reference points

    CP2105 Dual UART 1: $1.49 1,000: $1.30
    CP2104 Single UART 1: $1.43 1,000: $1.25
    C8051F387-GM 32K Flash USB uC 1: $1.74 1,000: $1.54
    FT23x FTDI start at 1: $2.04 1,000 $1.48

    Search for Microcontroller USB at Digikey finds also MC9S08JS8, PIC16LF1454, ATXMEGA16C4-AU,PIC18LF13K50
    all on a similar price curve.
  • joeysr20detjoeysr20det Posts: 8
    edited 2013-11-28 11:54
    Wow thanks for the constructive input MagIO2... I've been working in electronics for over 20 years, I'm well aware of the pros and cons of various microprocessors lol.

    Thanks for the heads up jmg I'll definitely look into these. I've been using Microchip PICs (the 18F series) and have gotten a custom to the hardware assisted USB stack :) I suppose a couple bucks might not be a bad.

    I've been looking at the FT200XD and FT201X from FTDI and these look pretty promising. If I decide to go this route with the Propeller, I'm definitely going to post my solution back to OBEX. I really enjoy this platform :)
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