PIC 16F876A RS232 Meter

by Nick Christodoulou

for the Olimex sponsored PCB contest

This is an evaluation development board for PIC 16F876A microcontroller. It consist of a 5V regulator, four pin headers connectors connected to each one PIC’s port, 20MHz crystal, MAX232 RS232 translator, and an ICSP (in circuit serial programming) connector. There is some code also written in assembly:

• RS232 communication routines between PC and PIC board (polling and interrupt)
• Simple blinking PIC port LEDs
• Analogue to Digital conversion using PIC16F876A internal available AD converter and transmitting the data readings to the PC via the RS232 port.

Also you can find the source code of a simple Windows application written in Visual Basic. This application receives and sends data from and to RS232 buffer, evaluates the voltage that the ADC reads and displays it.

Pin headers connectors connected to PIC port can be used for further application development. Now I am working for the building of a capacitor equivalent series resistor (ESR) measurement card witch will be connected to the PIC board.

Thank you
Nick Christodoulou
MSc Automation and Control Systems
GREECE

• Gerbers.zip
• PIC_code.zip
  • ASM
    • ADC_RS232.asm
    • ADC_RS232.HEX
  • R0 ADC (Most Significant 8Bits) to Port B
    • ADC_RS232.asm
    • ADC_RS232.HEX
  • R0 ADC sent to RS232 the measurement
    • ADC_RS232.asm
    • ADC_RS232.HEX
  • R0 ADC sent to RS232 with count
    • ADC_RS232.asm
    • ADC_RS232.HEX
  • RS232
  • HS 20MHz PC SENDS A BYTE (Interrupt) TO PIC PORTB AND PIC TRASMITED BACK TO PC
  • HS 20MHz PC SENT TO PIC (Interrupt) PORTB A BYTE
  • HS 20MHz PC SENT TO PIC (Polling) PORTB A BYTE
• Schematics
  • CPU
  • Power Supply
  • RS232 Port and I/O Connectors
  • Test points and LEDs
• VBasic_code.zip VBasic Windows application source code
  • rs232TRRS.frm

Update: Nick was kind enough to send along a correction to the entry. The VDD to MCLR blocking diode is not connected directly to MCLR pin but in series with MCLR pull up resistor like this:

This correction is easy enough to implement on the existing PCB: Just replace D1 with a wire jumper then use a surface mount version of D1 to form a little triangle with R1 on the pads originally for R1.