Described here construction of a universal development kit can be a great alternative for expensive factory development kits which often offer small number of functions or lack basic peripherals.
The most important advantages of the PCB are:
the possibility to connect any microcontroller in DIP housing to 40 pin or connect it to the board by means of cables of another system, such as ST Discovery with AVR etc
the possibility to power the PCB using one of five methods:
from USB ↔ UART converter
using microUSB sockets
using DC power supply 24V (without the heat sink on the voltage converter system)
from the programmer to the microcontroller or the circuit
directly from the DC power supply by providing voltage to the supply pins
the possibility to unlock the processor using the adjustable generator based on NE555 (you can use any generator)
3,3V power derived for pins, so that you can supply external peripherals from 3,3V
the possibility of service the device by yourself
the PCB is one-sided
it does not involve high voltages
List of components you need to create this development kit:
ZIF 40
voltage converter based on LM2576T-5
generator on NE555 with changeable frequency
temperature sensor DS18B20
LED bar (10 segments)
photoresistor RPP111
voltage divider for setting the voltage from 0 to VCC
EEPROM 24C04
USB<-> UART adapter based on MCP2200 with all GPIO lines derived
microUSB socket with all signals derived
5mm RGB diode
buzzer
microSD card
RTC
double H bridge
converter for the bus 485 and resistor terminating this bus
6 buttons
Attachment to the original thread contains schematic.