PIC18F252 Based Logic Analyzer

Figure 1 

Using the PIC18F252 or PIC18F2525 as capture device, the project was designed to build a low cost logic analyzer while showing the display on a Windows based PC.

The maximum rate is 2 microseconds in normal mode while limiting the sustained rate to 170 microseconds/event using RS232 or 40 microseconds/event using USB. The maximum sample rate is 200 nanoseconds in fast mode with 4-bit sampling at lower rates. The USB version of the logic analyzer is using a USB to RS232 converter interface.

In the design using USB interface, the probes are connected through a serial connector while a small PCB with the 18F252 is fitted in the center. The probe cable can become messy with loose wires but the color coding could be a great help.

In this logic analyzer design, a 4- or 8-channel digital signal logger for a PIC microcontroller can send its characteristics and samples a digital signal to a PC over a serial link. The recent modification of the circuit includes an 8-channel serial monitor option while monitoring only 7-bit data. Also added is the 5 and 10 usec sampling options in fast mode and redefined the command set for fast sampling with fixed timing bug.

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