Embedded System Visual COM Port Testing Card Design

This article detaily elaborate the design scheme of visual com port USB embedded system test card,this card can be for the small embedded system testing requirement.The whole testing system is composed by PC,test card and small embedded system which need to be the test.PC application software has the function of testing command transferring which based on SCPI protocol and test result display,USB port communicate with test card.Test card composed with USB port,ATMEGA32,level shift,ADC,DAC,I/O expand circuit,FTDI245 act as the visual COM port USB port.ATMEGA32 transfer parallel signal with FTDI245 and communicate small embedded system with SPI protocol.The article specify the test card ciucuit,PC application software and ATMEGA32 code design flow chart,also clarify the real time signal quality and HW debug procedure.And finally reveal the test card multifunction command instruction and simple,high efficiency SPI ptotocol which can be for the good reference of the same testing card design.