For radio engineers who like to design electronic devices, from time to time there is a need to use microcontrollers in their designs. The use of these semiconductor devices
opens huge prospects to the radio engineer. Microcontrollers are produced by only a few companies, the leaders of which are MicrochipTechnology, ATMEL, ARMLimited. The main feature of such devices is the need for their firmware. For this, programmers are needed. Today, there is a huge selection of different types of programmers, however, the price of such products is very high, and not every radio amateur can afford to buy such a device.
In this article, we will consider a USB programmer (AVR) based on the Atmega 8 microcontroller. This product is simple enough for a radio amateur to assemble it on his own and not spend a lot of money on a branded product. Our USB programmer (AVR) has a minimal microcontroller binding, which allows you to assemble a very miniature device. Such a product does not take up much space, it has the dimensions of a conventional flash drive. The USB programmer (AVR) in its circuit contains an Atmega 8 microcontroller , the type of housing is TQFP 32 (not to be confused with the type of DIP housing, since they have different pinouts). A diagram of such a device is shown in the photo.
We proceed to the description of the device circuit. Jumper J1 is used when it becomes necessary to flash a microcontroller having a clock frequency below 1.5 MHz. If desired, this jumper is easily excluded from the circuit, for this the 25th output of the controller sits on the ground. In this case, the AVR-USB programmer will always operate at a lower frequency. It should be noted that programming at a low frequency takes longer, but of course, you decide. Zener diodes D1, D2 are used to match the level between the USB-bus and the programmer. The blue LED indicates the readiness of the device for programming the microcontroller, the red diode is lit during programming. The circuit has an IDC-06 connector, on which contacts are output, the pinout of which corresponds to the ATMEL type of the 6-pin ISP connector. The power contacts of the microcontrollers are output to the indicated connector, it is taken from the USB port of a personal computer, therefore, it is necessary to be careful not to allow a short circuit. Using the same connector, the programming of the control controller takes place, for this it is necessary to connect the Reset contacts on the controller and on the connector (shown in red on the diagram).
The jumper for reducing the speed of the programmer and the connector for connecting the microcontroller are located at the end of the device. That's what a USB programmer (AVR) is, as you can see, everything is elementary.
After assembling the device, you need to flash the control microcontroller, for this I recommend using the PonyProg program. When programming, we start the crystal for operation from an external clock source of 12 MHz.
The USB programmer for AVR described in this article works with all microcontrollers such as AVR, allows you to flash them, watch the recorded contents of the device, erase chips, and change the configuration.