[dorkbotpdx-blabber] How does the AT90USB162 bootloader know of which method

Donald Delmar Davis ddelmardavis at gmail.com
Mon Jun 30 16:40:48 EDT 2008

The at90usb series has a fuse bit for HWB (hardware boot) and if the  
fuse is set then it checks to see if the HWB pin is pulled before  
entering either the boot section or the application section. This is  
pretty well described in the boot sequence section of the datasheet.

The chips come pre programmed with a boot section that is a Device  
Firmware Updater. It can be reprogrammed to do whatever. Dean Camera's  
MyUSB library has source code for a DFU bootloader and one that acts  
like an stk500 over a cdc device.

If in your search for more io you check out the 90usb647 family then  
plan on using deans bootloaders as the stock one is busted.

Thanks for the links. I am thinking about testing out one of the JTAG  
clones with the benito for the serial.

Since you have no fear of tqfp I suggest you check out the  
mega(16/32/64/)5 family as well as the at90usb64(6/7) all of them have  
the same footprint as the mega128 at a fraction of the cost. the  
larger usb parts require only 6 pin changes (the usb specific ones) to  
work with in the same place as the mega128.

On Jun 30, 2008, at 10:11 AM, Transistor Toaster wrote:

> I think I might have emailed this to myself but not the mailing  
> list, so
> pardon me if this is a double post.
> Hello,
> I was just wondering how does the AT90USB162 know which particular
> programming method is to be used? If I hold nHWB low and pulse the  
> line, how does it know it is supposed to talk to the PC with the USB
> port and not JTAG or ICSP?
> Frank
>> On Sun, 29 Jun 2008 13:09:24 -0400, "Transistor Toaster"
>> <transistortoaster at fastmail.fm> said:
>>> Hi,
>>> I'm a n00b just starting out with AVRS. I have been programming with
>>> FLIP the AT90USB162. I would like to know that if the benito5 only  
>>> has
>>> the capability to program another AVR but not to debug?
>>> Frank
>>> -- 
>>>  Transistor Toaster
>>>  transistortoaster at fastmail.fm
>>> -- 
>>> http://www.fastmail.fm - mmm... Fastmail...
>> -- 
>>  Transistor Toaster
>>  transistortoaster at fastmail.fm
>> -- 
>> http://www.fastmail.fm - Choose from over 50 domains or use your own
> -- 
>  Transistor Toaster
>  transistortoaster at fastmail.fm
> -- 
> http://www.fastmail.fm - A fast, anti-spam email service.
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