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Howto access bootloader

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About

The HP Jornada 710/720/728 with flashrom has an bootloader installed. This is what eventually starts the linux kernel. You can access the content of the flashrom through a serial port and your Jornada serial port.

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What is needed

  • Flashrom (with bootloader installed)
  • Jornada Serial Cable
  • Serial contact on your PC (or USB->serial adapter)
  • A serial communication software (like minicom or hyperterminal).
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Why would I want to access Bootloader?

You can do alot of things from there:

  • Kernel
    • Reflash/testboot(boot without flashing)
    • Userland (flash onto flashrom)
  • Debug Memory
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What Device(only for linux)

If you use a usb->serial dongle you will see something like this, when inserting it. Code: Select All 

      usb 1-3.3: new full speed USB device using ehci_hcd and address 19
      usb 1-3.3: configuration #1 chosen from 1 choice
      USB Serial support registered for pl2303
      pl2303 1-3.3:1.0: pl2303 converter detected
      usb 1-3.3: pl2303 converter now attached to ttyUSB2
      usbcore: registered new interface driver pl2303
      pl2303: Prolific PL2303 USB to serial adaptor driver

Device in example above is therefore /dev/ttyUSB2

If you are using a real serial connection on your computer then it will already be under /dev/tty.

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Serial Settings

Whatever serial solution you use (serial/usb->serial) you will need to configure the software so it works. Here are the main settings which the bootloader talks with: 19200 8N1

Heres a copy of my minicom configuration file: Code: Select All 

     pu baudrate         19200
     pu minit            
     pu mreset           
     pu mautobaud        Yes
     pu hasdcd           No
     pu rtscts           No 
     pu xonxoff          Yes
     pu macenab          No
     pu localecho        Yes
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Howto

1) Connect all serial cables, remove battery from jornada 2) startup serial software 3) connect power cord to jornada 4) press enter before it loads kernel

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