Using Rs232; Programming In-System - Atmel megaAVR Getting Started

Board Applications
9.6

Using RS232

9.7 Programming In-
System
9-4
Connection Name
D1
D2
D3
D4
D5
D6
D7
The board is designed for use with a LCD with a Hitachi driver chip built-in, with a con-
trast pin voltage of 0 to 5 Volts. The pot next to the LCD connector is used for contrast
adjustment.
If you use a different LCD driver, it may have a different voltage contrast range. In order
to accommodate this, add a resistor to the board (shown on board) and cut track on
underside of board—marked cut.
This board is not designed for use with back lit LCD modules, so the extra connections
needed are not included and the power supply will not supply the current required.
The LCD must be driven in Memory Mapped Mode as Read and Write are descite pins
on the Mega parts—see data sheet. If the crystal has been changed to a faster crystal
frequency, memory mapped operations will not work.
The connection supplied is a 9-way female D-type, so a straight-through lead is
required, not a null-modem cable.
The Jumpers in the middle of the board, marked PE0 and PE1 must be set to RS232,
not Port or RXD and TXD will be disabled.
As this board has a 4 MHz crystal, the percentage error on the Baud Rate will be
between 0.2 and 7.8%. Replacing the crystal with a 3.6846 MHz or 4.608 MHz crystal
will reduce this error to zero but may have EMC implications.
A standard (straight-through) lead is required, NOT a null-modem cable.
Devices can be programmed in your circuit rather than on the board.
For In-System Programming, ISP, the 10-conductor ribbon cable is connected to a dual
row 10-pin 0.1" pitch header on your circuit.
You will need to use either a multiplexer chip, such as a 4053, or wire directly to the pins
of the device. Without a multiplexer chip, Serial Communications and SPI port will be
unusable.
In addition, the system 5 Volts and Ground needs to be connected to the programming
lead.
DO NOT EXCEED 5 VOLTS ± 5% (4.75V TO 5.25V). YOU MAY DAMAGE YOUR
COMPUTER. THIS WARNING APPLIES TO ANY ISP SYSTEM.
Function
Data Bit 1
Data Bit 2
Data Bit 3
Data Bit 4
Data Bit 5
Data Bit 6
Data Bit 7
megaAVR™ Starter Kit Manual