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32 Bit Digital Output Board controllable via RS232 Serial / I2C
by Bryan A. Thompson
Last Updated 11/29/2008
This circuit provides 32 - 1 Amp digital outputs and is controllable via either RS232 or I2C. Connection is through four RJ45 jacks. The circuit uses a MAX233 level converter IC to connect the BL233 I2C generator to the host computer. RS232 commands generate I2C commands which are decoded and then latched via four 8-bit PCF8574 ICs. The outputs of the PCF8574s are connected to four ULN2083 Transistor arrays. The transistor array outputs provide a path to ground for the connected loads.
It is trivial to modify this circuit to be a RS232 to I2C converter, or to modify it to be driven by an I2C-capable microcontroller instead of a serial port.
Figure 1 - Schematic
Figure 2 - PC Boards
Download complete Eagle 4.x project and documentation (Click Here)