Homemade parallel port ISP download cable

Use a 244 chip plus a few resistors and capacitors. This AVR download line is supported in BASCOM-AVR, ICCAVR, CVAVR and the free Pony Head download software. It is safe and reliable. This AVR download line is used in the ATMEL laboratory of the Department of Electronics of East China Normal University. 
Thanks to choicesun for providing the most simplified design diagram. This circuit diagram has been tested under SLisp1.32 and PonyProg2000, and the download is smooth.

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Homemade AVR MCU ISP Download Cable The function of the MCU programmer is to burn the debugged program into the memory of the MCU. The cost of the AVR MCU ISP download cable introduced in this article is only about 10 yuan, which is very suitable for beginners to make. The program of the AVR MCU can be downloaded and written using the serial in-circuit programming (ISP) method, which means that the program can be burned and modified directly on the circuit board. The required device is an ISP download cable. The ISP download cable introduced in this article uses the parallel port of the computer to program the MCU. It not only supports AVR MCU, but also supports the programming of AT89S series MCU in 51 MCU.

      1. Download line circuit The circuit of the download line is shown in Figure 1. This download line is the STK200/300 type download line. 74HC244 is an 8-buffer circuit used for buffer isolation between the computer parallel port and the single-chip microcomputer.

       The LPT in Figure 1 is connected to the parallel port of the computer and serves as an interface for the download software on the computer to communicate with the microcontroller.

      Pins ④ and ⑤ of LPT are used to control the output of two groups of buffers. When the output is low level, the controlled buffer can transmit data normally; when the output is high level, the output end of the controlled buffer is in high impedance state.

      Pin ⑦ of LPT outputs programming commands and data to the MOSI terminal of the microcontroller (MOSI here means computer output and microcontroller input);

     Pin ⑥ of LPT outputs the serial programming clock signal to the SCK terminal of the microcontroller;

     The ⑨ pin of LPT outputs the reset signal to the RST terminal;

     The ⑧ pin of LPT outputs the programming status signal to the LED terminal. LED is a light-emitting diode on the target board and can be used. The information read by the microcontroller is output to the ⑩ pin of LPT via the MISO terminal (MISO here means microcontroller output and computer input). The power supply of 74HC244 is provided by the 5V power supply on the microcontroller target board through the diode VD1.    

     The download cable uses a 10-core wire and a standard 10-pin IDC connector. The top view of one end of the cable facing the connector is shown in Figure 2. Taking the AVR microcontroller ATmega8 as an example, the interface circuit when programming the microcontroller is shown in Figure 3. This is the minimum system of the Atmega8 microcontroller. Since the internal RC oscillator is used as the clock source, there is no external crystal oscillator circuit in the circuit. Therefore, it cannot be set to use an external crystal oscillator when setting the fuse bit.     

2. How to use the software The software used with the download cable includes PonyProg2000, ISPlay, etc. This article takes PonyProg2000 as an example to introduce how to use the software, and also takes ATmega8 programming as an example.    

1. Set up the ISP download communication interface Open the software PonyProg2000, click the "Set" button on the toolbar, select the radio button "Parallel" in the pop-up "Interface Board Settings" window, select "AvrISP I/O" in the drop-down list, click the "Test" button to check whether the interface settings are correct, and click the "Confirm" button to complete the settings.    

2. Select the device Select “AVR micro” in the first drop-down list on the toolbar and select “ATmega8” in the second drop-down list.    

3. Download operation Click the "Open" button in the tool, and the "Open Device Content File" dialog box pops up. Select "*.hex" in the "File Type" drop-down list. After finding the target file, click the "Open" button on the dialog box, and the target file will be loaded into the computer buffer. Click the "Write Device" button on the toolbar, and the "Yes or No" dialog box pops up. Click "Yes" to complete the program burning. The relevant operation interface is shown in Figure 4. If the device to be written has been written with a program before, click the "Erase" button on the toolbar to erase it before rewriting the program.