wiki:USB-POV_Test_Log

'2011-12-04

  • Solder programming cable onto prototype board for AVRISP II (include 10k pullup on nRST)
  • Compile USBaspLoader, enumerates correctly with Makefile,
  DEVICE = atmega88p
  AVRDUDE_DEVICE = m88
  BOOTLOADER_ADDRESS = 1800
  FUSEOPT = $(FUSEOPT_88)
    ...
  AVRDUDE = sudo avrdude $(PROGRAMMER) -p $(AVRDUDE_DEVICE)

In bootloaderconfig.h:

  #define HAVE_EEPROM_PAGED_ACCESS    0
  #define HAVE_EEPROM_BYTE_ACCESS     0

(without the above apparently the loader is too big... maybe not true?)

Default behavior is to not enter boot loader on power-up reset. Comment out the following to disable:

 // if(!(MCUCSR & (1 << EXTRF)))    /* If this was not an external reset, ignore */                                                   
 // leaveBootloader();                                                                                                            
 //  MCUCSR = 0;         

Also the following to force boot loader on every time:

  #define bootLoaderCondition()   (1)

OK, now on power-up we always get the boot loader. Can exit it by just running AVRdude with no operations:

  sudo avrdude -c USBasp -P usb -p m88

Then the app starts. Desired behavior would be boot loader if USB is plugged in. Must be a way to do this in software...

In main.c, function 'initForUsbConnectivity() doesn't do much. It is the 'usbPoll() call we have to focus on. In main.c we have the loop:

 do{
   usbPoll();
   if(requestBootLoaderExit){ ... }
 } while(bootLoaderCondition());  /* main event loop */

Modify as follows, to automatically sense if USB is connected at power-up and start the boot loader.

  wasUSBActivity = 0;
  ...
  if(bootLoaderCondition()){
    uchar i = 0, j = 0;
    initForUsbConnectivity();
    do{
      if( !wasUSBActivity)
        if(++countIdleUSBLoops > 1000000)
          leaveBootloader();
      usbPoll();
      if(requestBootLoaderExit){ ... }
     }

Also declare countIdleUSBLoops as long, and set wasUSBActivity = 1 in usbProcessRx() in usbdrv.c. With 1e6 loops as above it has about a 5s time-out.

Last modified 6 years ago Last modified on Nov 8, 2013, 10:17:53 AM