For people who like to design electronic devices, sooner or later there is a need to use microcontrollers in their designs. The use of these devices opens up enormous opportunities for the radio engineer. Microcontrollers are manufactured by only a few companies, the leaders are Microchip Technology, ATMEL, ARM Limited. A feature of such devices is the need for their firmware. That's what programmers are for. There are many types of these devices, you can buy a branded one, or you can do it yourself. If you chose the second option, it is best to use a ready-made and proven solution, such as the Gromov programmer. The device is quite simple, even a beginner can assemble it.
COM (AVR) -gromov programmer
COM programmer is easy to manufacture. If you use the alternative mode of the "COM" port of Bitbang, it becomes unnecessary to convert the RS232 interface of the COM port to SPI, which is necessary for programming. It remains only to coordinate the signal levels in the COM port, from -12V, + 12V to 0V and + 5V. For this, the programmer circuit for AVR controllers is intended. The photo below shows the Gromov programmer.
This scheme was first proposed by the author of the AlgoritmBuilder program, Gennady Gromov, and quickly gained popularity with its reliability and ease of execution.
In order to proceed with the assembly of the device, we need:
- Diodes KD510, KD522, 1N4148 or their analogues.
- Seven resistors with a nominal resistance of 1 kOhm, power does not matter.
- Loop - you can use an unnecessary computer IDE loop. For more stable operation of the programmer circuit, it is necessary to alternate the signal wires with the neutral wire. So we can reduce the level of induced noise in the circuits, as well as lengthen the programming wire. However, do not get carried away, the length of the loop should not exceed 50cm.
- A connector for connecting to a programmable device, you can use standard connectors (by the way, microcontroller manufacturers also recommend it), or you can use a connector like BLS (“mother”), with the same connectors on computers on the motherboard, case buttons and LEDs are connected and pins like PLS (“dads”). The use of these connectors can significantly simplify the device board, since the pins of the programmer are located in close proximity to the legs of the microcontroller. The SCK, MOSI, MISO contacts of the AVR type microcontroller are located together; accordingly, a built-in connector should be used for them. Separately connect the "ground" and "reset".
As you can see, everything is very simple, this is what Gromov's programmer is valued for.
For the operation of this device, a program and test firmware for the microcontroller are required.
Gromov's universal programmer is assembled on passive elements. It does not require a separate power supply, and most interestingly, due to the parasitic voltage arising in the circuit, microcontrollers can be programmed without connecting to a power source.
Using the same principle, you can also build a usb programmer, but the circuit of such a device is somewhat more complicated.