P-Star 25K50 Micro on a breadboard with a reset button (left) and a bootloader
button (on-board).
The bootloader button can be used for other purposes while your application is running. However, be
careful to never drive the RB6 line low, or else pressing the button could cause a short circuit.
Starting the bootloader from your application
The bootloader can also be started by the application without requiring a reset. To do this, the
application can simply jump to address 4 using the assembly instruction
goto 4
. If the application
uses USB, it should disable the USB module by clearing USBEN and then wait for at least 100 ms
before starting the bootloader in order to give the computer time to detect that the application has
disconnected.
For convenience, we recommend that any P-Star applications with a USB interface implement a USB
command for starting the bootloader. This would allow you to get into bootloader mode, upload the
new firmware, and run it, entirely using USB and not needing any physical interaction with the board.
For example, an application with a USB virtual COM port could listen for a special baud rate to be set
Pololu P-Star User’s Guide
© 2001–2019 Pololu Corporation
5. Getting started
Page 18 of 46
