Wiblocks --- ZB1 Changes

ZB1 Reset Circuit Changes

The reset circuit on the ZB1 boards, Rev 1 and Rev 2, consists of a 0.47μF cap in parallel with a 10KΩ resistor. The recommendation from Atmel (AVR042) is to parallel a diode with a 10KΩ resistor as shown in the Reset Circuit ECO schematic on the right. This is an easy change to make on the ZB1 board.

Making this change will enable the reset capacitor, C13, to reset the board when if your USB port is setup to set RTS on close. In the original circuit, C13 could not pull the RESET line to a low enough voltage to reset the ATmega microcontroller. Removing 0.47μF of capacitance from the RESET pin enables C13 to pull the voltage on the RESET pin below the reset level.

C6 provided noise supression and transient surpression. Since the RESET pin does not have a protection diode should be added when C6 is removed. Atmel also recommends an optional noise supression capacitor in from the RESET pin to ground. This should not be necessary for the ZB1. The only connection to the RESET pin is to the ICSP header. Since most applications do not permanently wire the ICSP header the RESET line should not be noisy.