1. CMYK
CIRCUIT
IDEAS
ATMEL AVR ISP DONGLE SANI TH
EO
EFY LAB grammed is sent on this pin parallel port.
3. SCK (Shift Clock): Serial clock IC 74LS244 (IC1) acts as a buffer as
A
tmel’s AVR microcontroller generated by the programmer from the well as an isolator circuit when the
chips are in-system program- PC. AVR is not in programming mode. In
mable (ISP), i.e. these can be 4. RST (Reset): Reset (low pulse) idle mode, all the outputs are tristated
programmed directly in the target cir- generated by the program. The AVR so as not to affect the operation of the
cuit. A special programmer software is programmed while in reset state. target system.
is used to download the program from Here’s a dongle circuit for in-sys- When the AVR’s ISP mode is se-
the PC into the AVR’s flash memory. tem programming of Atmel’s AVR chip lected, the lower half of IC 74LS244
Atmel offers a software package called AT90S8515 using such software pack- is enabled, pulling the target system’s
the Atmel AVR ISP that allows pro- ages as Atmel ISP 2.65 and Reset line low. Once the target
gramming of the AVR microcontrollers PonyProg2000. Though not exactly the system is in Reset mode, the SCK,
in the circuit using a simple dongle. A same, a similar dongle circuit can be MISO and MOSI lines are no longer
dongle is nothing but an adaptor cable found at the Website ‘www.iready.org/ loaded by the peripheral circuitry, if
that connects the PC’s parallel port projects/uinternet/ispdongle.pdf.’ any, on the target system. Now, it is
with the ISP pins of the AVR chip for The PC’s parallel-port pins 4 and safe to enable the upper half of
programming. 5 drive buffer IC 74LS244 by enabling 74LS244, driving the MOSI, LED and
For programming, the four lines re- its pins 19 and 1, respectively. A low SCK lines of the dongle. The RST pin
quired from the AVR chip to the ISP pulse on these pins will allow the becomes high after the AVR is pro-
adaptor (dongle) are: passing of the serial clock and data grammed. Glowing of LED2 indicates
1. MOSI (Master Out, Slave In): during programming. MOSI, LED, that the AVR is in programming mode.
Data being transmitted to the AVR be- SCK and RST outputs are buffered There are two standard connectors
ing programmed is sent on this pin from the parallel port’s pins 7, 8, 6 for in-system programming of Atmel
2. MISO (Master In, Slave Out): and 9, respectively. The MISO input AVR microcontroller. One is the 10-
Data received from the AVR being pro- from the AVR is fed into pin 10 of the pin header (dual-in-line (DIL) connec-
100 • FEBRUARY 2005 • ELECTRONICS FOR YOU WWW.EFYMAG.COM

2. CMYK
CIRCUIT
IDEAS
tor)) used on the Atmel STK kits. The the dongle is identified as a value- 6-line cable of about 30cm length is
other is a 6-pin header (DIL connec- added pack dongle. required for connecting this ISP adap-
tor) used in Atmel ISPs. The two loop- Here, we’ve used an 8-pin single-in- tor (dongle) to the target circuit.
back connections, pin 2-to-pin 12 and line (SIL) connector and an additional If the AVR is not on the target cir-
pin 3-to-pin 11 of the parallel port, are 6-pin SIL connector for the Atmel pro- cuit, you can insert the AVR into the
used to identify the dongle. With only gramer circuit. With the buffer and the ZIF socket and program it. Regulated
pin 2-to-pin 12 link, the dongle is 40-pin ZIF socket in this circuit, it can be 5V DC is required for the AVR and
called STK300 or AVR ISP dongle. used as a standalone programmer. The the associated dongle circuit, whose
With only pin 3-to-pin 11 link, the 6-pin SIL male connector is used for terminals are also provided in connec-
dongle is called STK200 or old Kanda connection between the dongle and the tor CON4. LED1 is used as the power
ISP dongle. With both links in place, AVR on the target board. Thus, another indicator for the circuit.
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