JPWR (Power Selector) – is used to configure the power source for the board. When the jumper is connected, the board is self-powered (the power for the board is supplied by the PC parallel port). When the jumper is removed, the power must be supplied through the V+ pin. The voltage must be in the range of 0.9V to 5.5V. PWR (Power Indicator) - is used to visually show there is power to the board. The LED may not be illuminated when a low voltage is applied to the board. The LED turns on when a voltage of greater than 1.8V is applied to the board. Trigger Out - is a general purpose Output pin that can be used as a trigger output embedded into an i2c message. Input Port - is a general purpose Input pin. A0 (EEPROM Pin 1) - is usually the Address 0 (A0) address bit. This jumper allows the user to change the on-board EE address. WP (EEPROM Pin 7) - is usually a Write Protect (WP) input and may be active either high or low. This jumper allows the user to put the WP pin in the correct state for writing. You can also place a device like the PCF8570 static RAM in the EEPROM socket and then tie this pin low. EEPROM - is socketed to allow the user to use this hardware to program DIP EEPROMs. The EEPROM is a handy feature to verify the hardware/software are functioning correctly. Headers - there are two headers on the board with different pinning layouts to connect the LPT-to-I2C SE hardware to the user's target system.
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DB-25
Parallel Port Connector - plugs into the computer’s printer
(LPT) port.
This
figure shows the low voltage capability of the new LPT-to-I2C SE
hardware. The i2c signal is 0.9V at 100 KHz.
