MT-DB-U2
Manual
Jumper
Mode
Driver
No
User Program
CDC (COM port) (
optional
)
Yes
Bootloader Program
CDC Serial/DFU Bootloader
It is not necessary to remove and replace the jumper when switching between the bootloader
and the user application. The jumper can be left on. After FLASH programming, the CDC bootloader
will automatically jump to the application. If using the DFU bootloader, then you can command FLIP
or dfuprogrammer to jump to the application. Then, when running the application, the reset button can
be pressed to reenter the bootloader. This is useful when writing and debugging firmware. When the
firmware is complete, the jumper can be removed so that future resets will always run the application.
The pins associated with the LED, jumper, and reset button are all routed to header pins. The
LED can be disconnected by unsoldering jumper J2. The jumper is connected to pin D7 on one side
and to ground through a 240 ohm resistor on the other side. There is a 10K pullup on the reset line.
ISP Header
The ISP header is configured by default to allow ISP programming using an external
programmer. That is, RESET is routed to pin 5. Pin 1 is marked on the board (it is the pin closest to
the chip). The ISP header can be reconfigured so that pin PB0 (SS) is connected to pin 5 rather than
RESET. This can be done by switching solder jumper J1. This allows the MTDBU2 to be used as an
AVRISPmkII programmer itself, using Dean Camera's AVRISPmkII software available at
http://www.fourwalledcubicle.com/
. A precompiled hex file will be made available at
on the MTDBU2 product page. Note that when using the ISP header in
this way, Vcc and ground are output to the target board. Therefore, the target board should not be
powered itself. You should also verify that it is safe to power the target board through the ISP
connector. Another use for the ISP header configured with SS on pin 5 is to make use of SPI, either as
a master or slave. SPI can also be used on the normal DIL headers. When using the ISP header, you
may need to remove the HWB jumper to allow the ISP connector to fit.
October 29, 2015
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