I've used bootloaders for other uC families, but not for AVR. Is there a protocol standard? If not, how does one get Atmel Studio to live with a given standard as executed by a particular boot loader?
Is there tweakable bootloader code I should be starting with?
The target here will be an educational device built around the ATmega640/1280, which has serial ports out the ear, so I thought I'd use one for a bootloader interface, along with standard ISP.
stevech 
Atmel has several bootloader standard formats. They have changed over the years. Among the oldest is app note AVR109 as I recall.
AVR chips do not come with a pre-programmed bootloader. If you purchase certain end items, say, an Arduino board, they will have written to flash, in the AVR's special space for bootloaders, that world's standard bootloader. If you buy a Teensy2 from PJRC, they have their own (terrific) USB based bootloader. And so on.
To put a bootloader of your own choice into an AVR, perhaps replacing what's there now, you need an In System Programmer (ISP). That uses the MOSI, MISO and so on interface, and an ISP programmer such as the Atmel MK-II.
As a beginner, I'd recommend the Teensy2 since you can use that for arduino and non-arduino code work, with the Arduino development IDE or Atmel Studio 6 or any of the commercial compilers for AVR.
http://www.pjrc.com/teensy/index...
Here's an oldie bootloader, serial port, as an example. This freeware has both the AVR code (small, asm, source provided) and the PC side with graphical user interface.
https://www.avrfreaks.net/index.p...
So lots of alternatives.
clawson 
AS4 used to come with "Avrprog" which was used for things like talking to the Butterfly and the STK500 bootloader. It talked AV109 protocol so that seemed like a good choice to base a bootloader on (it was fairly simple so an Asm bootloader could just about fit into 512 bytes).
AS6 seems to have lost avrprog (I don't think atprogram handles 109) - there's certainly nothing available from the GUI interface to invoke 109 protocol anyway.
So I guess AS6 announces the death of AVR109?
The next protocol that may be worth looking at is the one that would make the AVR bootloader look like an STK500 in CTRL mode. There was originally an "stk500" protocol but this was updated and these days an STK500 talks "stk500v2" protocol. A lot of non-Atmel programmers talk this same protocol which is why you get all those programmer interfaces on ebay that call themselves "STK500" when they have nothing to do with an STK500 but simply use its communication protocol (thankfully those devices are now replaced by USBAsp's in fact).
stk500v2 is described in AVR068
Luckily for the world there is already an STK500 v2 template bootloader:
http://homepage.hispeed.ch/peter...
(towards the bottom of Peter Fleury's page).
I *think* you can therefore tell AS6 through the GUI you are programming via STK500 and it will channel via that bootloader.
Another option would be DFU which (for USB devices) is now Atmel's chosen bootloader format but curiously they don't ship the PC side of this (Flip! - a Java program) with AS6. This may be because they are too embarrassed as it is a POS.
Of course, if you are willing to forgo Studio compatibility then the world is your oyster (and avrdude can talk to most bootloaders).
Shameless plug: If you were willing to put an SD card slot in the design you could use this: http://spaces.atmel.com/gf/proje... ;-)
When I was teaching at a University, we used Steve's BLIPS 4. Hundreds of ATMEGA12's were used by students with no problems since then.
Thanks for all the info so far. So is it the case that Atmel Studio cannot program an Arduino via the latter's bootloader? If true that is an appalling oversight.
As I mentioned, this is an educational application, so whatever is easiest to do from AS6 is probably what I will go with.
clawson
So is it the case that Atmel Studio cannot program an Arduino via the latter's bootloader?
If true that is an appalling oversight.
As I mentioned, this is an educational application, so whatever is easiest to do from AS6 is probably what I will go with.
The arduino Uno uses a subset of stk500v1 (which is old, and is actually a "device programmer" communications protocol rather than a bootloader protocol.) Avrdude has gradually been updated to consider it a special type, in order to get around other changes in avrdude, and to support the auto-reset capability.
Arduino MEGA uses a stk500v2-based bootloader (it's only 16x bigger! (It does include significant extra functionality.))
This is great, I have no room for a 4K BL so without this I'd be updating manually (take chip out- move to computer etc etc).
It works and updates the flash, but does not find the correct sector for the file data. The SD is a 2GB Fat16 formatted.
lba = firstclust - fat_offset; //lba=1 lba *= SecPerClus;// lba=64 lba += RootDir;//lba=672 RootDir=608
The lba=672 is incorrect, it should be 640, so adding lba=640; after the above code is the only way it works at present.
david.prentice I don't see what a "file system" has got to do with a bootloader.
The Arduino UNO bootloader is only 512 bytes. It uploads programs to the flash memory via the UART / USB cable.
Yes, you can have a bootloader that can upload from an SD disk. But obviously you need a SD disk.
I think that Cliff (clawson) has a suitable bootloader. I suspect that it will need all of 4kB.
But let's face it. If you have a SD card in your product, you can offload data / text from flash memory and read it from the SD card.
David.
bobgardner I edit up a bat file that has the avrdude comport and baudrate params and the filename being burned. After compiling, I just click on the bat file and the program slides down the wire and jumps into the avr.
stevech
Atmel Studio 6.x with the free Visual Micro plugin can program AVRs via AVRdude.
The AVR should have optiboot or any other STK500 compatible bootloader firmware.
clawson I think that Cliff (clawson) has a suitable bootloader.
David, it's my code he's talking about - he's cross posted this - I have answered in the more appropriate thread.
(to be honest I *thought* I was implementing fatgen103.doc correctly but OP has discovered a case that seems to have exposed a flaw in my logic).
