Play the AVR HyperTerm
during programming; it needs a crystal or
ceramic resonator, CR1, for data movements.
Power supply for the programmer is
drawn from a 9-12 V wall wart via a 78L05
voltage regulator to produce 5 V. Capacitor
C1 is used for smoothing. C2 is for resetting
U2. C3, C4, and the 3.6864 MHz crystal
provide the micro with the required working
frequency. LED1 is used to indicate the
circuit’s working status. C5 is for decoupling.
That is all there is to the programmer circuit description. It’s quite simple, consisting
of only two small chips. The AVR’s serial J2
interface makes it easy to program and there
are still alternatives for the circuit. For example, you can use a MAX232 if you don’t have
a DS275 on hand; also, you can use another
8051 micro for U2 — such as AT89C51/52
or P87C51/52. The only drawback is that
these chips are bulky, but they work just fine.
C3 27pF 4 XTAL2
The construction for this programmer is
also quite flexible. Depending on what chips
and materials you are going to use, you can
build it different ways: on a solderless breadboard, a perforated board, or using a PCB
(Printed Circuit Board).
For the people who prefer to build a permanent gadget,
you can download the foil patterns of a double-sided PC board
from the Nuts & Volts website at www.nutsvolts.com You
can make your own PCB or get one from
the source given in the Parts List. By
inspecting Figure 1 and the PCB layout,
it’s easy to identify each component’s
location and orientation or polarity.
When inserting a diode or electrolytic
capacitor into the PCB, care must be
taken not to make a polarity error.
The AT89C2051 (U2) must be
programmed before mounting it on the
board. The firmware is an Intel hex file —
AVRTMP1A.HEX — which can be downloaded from my website at www.geo
cities.com/xumicro. You can “burn”
this chip with the firmware file if you
have an 8X51 programmer; otherwise,
you can purchase it with the PCB.
For either building it on a perfboard or PCB, the basic principles are
the same. Depending on your programming and financial considerations, it can be built in either a deluxe
version or an economic version. For
the deluxe version, use solder-tail IC
Figure 2. The AVR Hyper Term schematic.
sockets for chip U1 and U2, but a 20-pin ZIF (zero insertion
force) socket for the AVR MCU. Because the ZIF socket
costs about $10.00, you can replace it with the regular
Figure 3. Adapter circuit.
Figure 4. LEDAVR hook-ups.
1 RESET Vcc 8
2 X1 SCK 7
3 X2 MISD 6
4 GND MDSI 5