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Versatile Centronics/I2C Interface

with logic analyser

Based on a Labs project | October 2011 | Find it here
When this interface is connected to an extended parallel printer port (EPP), your PC can communicate using the I2C protocol, and it can also make direct read and write accesses to eight data bits.Most of the I2C interfaces that have been described in Elektor Electronics up to now are based on a Philips application note. This circuit is no exception. However, its special feature is the combination of an I2C interface with an 8-bit parallel interface. The parallel port of the PC can be used for control, since 8-bit output was defined for this port by IBM from the very beginning. However, since the data lines were only intended to be used for output, it used to be necessary to resort to a trick in order to read in data. This consisted of using the status port of the interface to read data. Since the status port is only five bits wide, data had to be read in 4-bit nibbles.
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Component list
R1 = 22k?
R2-R9,R11,R12 = 10k?
R10 = 1k?
C1 = 10nF
C2 = 10µF 63V radial
C3 = 470F 25V radial
C4-C7 = 100nF ceramic
D1 = LED, high efficiency
IC1 = 74LS245
IC2,IC3 = 74LS06
IC4 = 7805
K1 = 25-way sub-D plug (male), PCB mount
K2 = 26-way boxheader or pinheader
B1 = B80C1500 in round case (80V piv, 1.5A peak)
PCB, order code 000096-1
Project software on disk, order code 000096-11
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