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.