Atmel megaAVR, Getting Started

Page: 23 / 28

Board Applications
megaAVR™ Starter Kit Manual 9-5
9.8 ISP Header
Layout
9.9 Interface Using
Resistors
Typical resistor values would be 1K. This circuit is fine if ports PB7, PE0 and PE1 are
used as inputs in your circuit and no communication is required. If Outputs are needed
or RS232 connections, especially higher than a few milliamps, then the multiplexed cir-
cuit is preferable.
9.10 Using an
Analogue
Multiplexer IC
The multiplexer select can be driven from the LED connection on the programming lead,
as can a low power LED with its cathode connected to the LED connection via a suitable
resistor. 1K
Ω
is fine. If you use this connectio, then the output will be low 0 during pro-
gramming and a 1 at all other times. Note that it will float if the programmer is not active,
i.e., the software is not running, so you may need to use a pull-up resistor.
KEY WAY
OPTIONAL PROGRAM
INDICATOR CICRUIT
PROGRAMMING HEADER
MISO IS CALLED PDO AND
MOSI IS PDI ON MEGA
DEVICES - PORT E BITS 0 AND 1
NOT PINS ON PORT B.
USER
CIRCUIT
TO ISP
CONNECTOR
TO USER
CIRCUIT