build usb interface

Lio · Post by **Lio** » Tue Apr 01, 2008 2:33 pm

hello
I wanna know what are the differents steps to build an usb interface with obdev firmware. Firstly i must build an bootloader with the AT902313 and it's here that I need help, i must load the firmware with witch software ? and if I wanna modify the firmware how can I make ?

Post by **christian** » Tue Apr 01, 2008 9:31 pm

First you need an AVR programmer. If your computer has a serial or parallel port (not USB adapters!), then you can build one of the simple programmers consisting of wire connections only.

If your computer has USB only, build USBasp, a simple USB programmer. You still need another programmer for this first AVR, though.

Once you have a programmer, you can build your target hardware. If you don't want to use the programmer every time to flash new firmware, put a bootloader on the target. The bootloader is a kind of integrated programmer -- the target programs itself. Most bootloaders take up 2k of the target's flash.

Lio · Post by **Lio** » Wed Apr 02, 2008 2:45 pm

Ok, I thought that USBasp was a bootloader, with it I don't need to implent the firmware in my µP with the lpt port ?? directly with the USB ?? and if it's with the usb I must use Avrdude ??

Lio · Post by **Lio** » Sun Apr 06, 2008 7:42 pm

And I have only usb port on my computer, witch interface must I build and what are exactly the differents steps for a good working.
thanks

Post by **christian** » Mon Apr 07, 2008 10:00 am

I would recommend that you build USBasp, since it's simple. You could consider the metaboard variant at http://metalab.at/wiki/Avrprog-metaboard because it has programming sockets.

You still have to flash your first AVR with other means, though. I'd recommend a simple parallel port programmer on a desktop PC for this purpose.

Guest · Post by **Guest** » Mon Apr 07, 2008 11:31 am

If I have understand before to build USBasp I need to build an programmer for the parallel port witch program the AVR and it's after that than I will can put the AVR on the USBasp board , and it's on the parralel programmer that I put the firmware on the AVR and it's with WINAVR that I can compile the firmware ? and with AVR DUDE I drive USBasp ??

Post by **christian** » Mon Apr 07, 2008 12:26 pm

Yes, that should be the procedure. You can also use avrdude for parallel port programming, not only for USBasp.

Lio · Post by **Lio** » Mon Apr 07, 2008 1:54 pm

So it's the same procedure that igor cesko interface, I thought that we implent the firmware with USBasp directly with the usb linkand not parallel port.

Lio · Post by **Lio** » Mon Apr 07, 2008 1:56 pm

And how you develop some applications with it ? e.g light led ?? with the HE10 port ?

Post by **christian** » Mon Apr 07, 2008 4:14 pm

Regarding the previous question: You need the parallel port programmer only ONE TIME, when you program the AVR for your USB based programmer. Once that is done, you use USBasp on the USB port and no parallel port is needed any more.

Regarding application development please see various examples on the net.