INTERFACE TO PARALLEL PORT
A project of connecting
analogue signal to LPT printer port. Included a VB6 software and
a circuit diagram. The ADC0804 is an 8 bit analogue to digital converter.
74HC4052 multiplexes the 8 bits output of the ADC into 2 data lines,
it is needed because most LPT's have only 5 input lines. 74HC4052 can be replaced by 4052B CMOS.
You can read more about LPT interface in http://www.beyondlogic.org/spp/parallel.htm
The VB6 software includes a freeware DLL (inpout32.dll) from http://logix4u.net/
VB6 code (30KB). Keep the .exe file and .dll in the same folder. You are free to use the circuit diagram and the VB software with no
The VB6 application is a combined digital and analogue
See also Technical Tips
5 volt supply can be an external
power supply, using the hosting computer 5V is much preferred because
variation between the computer 5V and the external 5V can lead to
undesirable currents through the data lines. 5 volt supply is available
at a USB port or the 4 way peripherals connector from the internal
power supply unit.
10k resistor and 470pF are for setting the internal clock of the
Input at pin 6 of the ADC is 0 to 5 volts full range positive voltage
only. The chip over voltage protection is 30V max.
Pins 2 and 3 of LPT select the 2 out of 8 bits to be read. Pins
15 and 13 read the selected 2 bits. Pin 1 initiates the ADC.
74HC4052 can be replaced by 4052B CMOS 4000 series.