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Re: [avr-gcc-list] usb programmer

From: Reza Naima
Subject: Re: [avr-gcc-list] usb programmer
Date: Tue, 22 Jul 2003 19:11:03 -0700
User-agent: Mutt/1.4i

I'm not sure if this is what you're interested in, but I've built a
circuit using the FTDI usb driver chipset and wrote appropriate
bootloader code and unix (tested on linux and macOsX) CLI programmer for it.
In theory it should work with all bootload-capable AVR ICs.  Email me if
you want an advance copy -- I've been meaning to clean it up before
posting it.  It's decently fast, sends data, compares checksum with
data, programs, and verifies that it has been programmed properly. It
should be easy to modify it to use a serial interface as well.

It can access pages using random access and I've been meaning on
building a 'diff-aware' tool to upload only modified pages to increase
programming speed.


On Wed, Jul 23, 2003 at 08:29:01AM +1200, Jason Kyle sent me this...
> At 15:07 22/07/2003 +0200, Joerg Wunsch wrote:
> >As Jason Kyle <address@hidden> wrote:
> >
> >>>If all else fails, how about using an USB-to-RS232 dongle, plus an
> >>>AVR910-style serial programmer?
> >
> >>I can't think of any reason why an STK500/AVRISP protocol programmer
> >>wouldn't work either.
> >
> >Me neither, except i thought they are more complex/expensive than a
> >simple AVR910-style one (which includes pAVR, if i'm not mistaken).
> Yes, that's true.  The AVR910 protocol was originally implemented on an 
> AT90S1200 (i.e. no SRAM) and hence programs one byte at a time and 
> acknowledges.  Now this makes it painfully slow since the 2 characters sent 
> in an ack may take several ms to arrive back at the programming software 
> due to OS delays and also the software itself.  If you were to program a 
> mega128 you'd have time to walk the dog before it finishes!
> STK500 protocol sends 256bytes at a time (and at 115.2kbps) so there are 
> 255 less ack transmissions made than AVR910 sending the same amount of 
> data, this alone makes the programmer way way faster.
> To put this in context with usb-serial adapters, there are a few 
> manufacturers and they don't all do exactly the same thing when it comes to 
> forwarding received data to the PC.  All of them have some kind of receive 
> FIFO and if it isn't full (e.g. 2 byte ack from an AVR910) they will have a 
> timeout delay of some number of ms (early FTDI usb-serial chips were 16ms, 
> later ones are variable down to 1ms) so we have slower programming than 
> over a standard 16550 UART serial port.  Depending on the usb-serial 
> adapter you might have a lot of free time on your hands :)
> So although STK500 is a more complex protocol it would be the best choice 
> for use over a usb-serial adapter.
> Jason Kyle
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