The latest release of Arduino IDE (v1.6.8) has introduced a problem that
prevents sketches from running on many chipKIT boards, in addition to
some Arduino boards. It appears that any board using an FTDI chip for
serial bootloader communications is adversely affected.
A temporary solution is to re-install the previous version, Arduino IDE
v1.6.7, which has been well-tested and known to work fine with
chipKIT-core selected in the Boards Manager. For more information about
installing Arduino IDE and chipKIT-core, refer to the
chipKIT-core Wiki page.
When the problem with v1.6.8 occurs, the sketch compiles and downloads
from the IDE just fine, but does not appear to execute on the chipKIT
board. This is because the serial DTR line between the FTDI chip and MCU
is being toggled approximately once per second. DTR is typically tied
to the MCU’s RESET line, causing the board to reset before the sketch
has had a chance to execute.