62 lines
2.6 KiB
Plaintext
62 lines
2.6 KiB
Plaintext
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Default settings are designed for atmega8 (with external 16MHz crystal)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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First you have to bring the USBaspLoader into the MCU by some conventional
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way, for example by using the traditional LPT1 on an old computer:
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--> avrdude -p m8 -c pony-stk200 -e -U flash:w:bootloaderfirmware.hex <--
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Or via an already existing MCU, flashed with the USBasp Programmer:
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--> avrdude -p m8 -c usbasp -e -U flash:w:bootloaderfirmware.hex <--
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If you already have an existing (and spminterface supporting) USBaspLoader
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flashed and you just want to update the loader to new features/version,
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you can use its integrated update-feature by flashing the update-firmware.
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After executing it at least one time, it will replace the old loader with
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the new one contained within the update. Then you can start flashing other
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firmwares, again...
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Since the atmega8 (used as default) is 5V, the recommended USB-Schematics
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should use zeners. (for more information see the VUSB designrecommendation
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with the two 1N4729 zener diodes as level limiter...)
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Because it is most unlikely to use the atmega8 as analogous comperator
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(there are much more cheap ICs for this), it is recommended to use those
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PINs for USB-Interface (this is the default, but it can be changed):
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USBD+ (green) --> PIN4 (PD2) (usually INT0 PIN)
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USBD- (white) --> PIN13 (PD7, AIN1) (new since Rev.3)
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BUTTON SWITCH --> PIN12 (PD6, AIN0) (new since Rev.3)
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Since the PD6 and PD7 lines were swapped in example board revision 3,
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it is possible to use the internal analogous comperator module, too.
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(Since AIN1 can be remapped to an other PIN but AIN0 not.)
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Now having the BUTTON SWITCH on AIN0 allows external connections to
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this PIN. Before Rev.3 (Rev2 and older) this was not possible, since
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USBD- needs to be exclusive and is not routed to an external PIN on
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the board. (Now USBD- is on AIN1, which can be remapped.)
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The bootloader bootup logic has changed a little bit, compared to the
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original JUMPER-logic within original USBaspLoader 2010-07-27.
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However most of the new logic is compatible with old JUMPER schematics:
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When RESET/PowerUP while BUTTON is pressed (PIN12 is low), then bootloader
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will start. Even if the BUTTON is release after this and PIN12 becomes HIGH,
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the bootloader stays active and listens to commands as long as the BUTTON
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will be pressed (and so PIN12 becomes low) again...
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If the BUTTON is NOT pressed at RESET/PowerUP, or pressed again while
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in bootloader, the user defined firmware is started.
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for default atmega8 recommended MCU-settings are:
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LFUSE: 0x1f
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HFUSE: 0xc0
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LOCK : 0x3f (unchanged - the bootsection is proceteced via loader software)
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