MSP430 Launchpad connection of photoresistor and concerns regarding Launchpads protection
I think you may be getting confused between the two devices.  With an LED a resistor is required to both protect the LED and the MCU's IO pin.

For a photo-resistor (I assume you mean something like an old Cadmium Sulphide Cell?) it is just a resistor which changes its resistance according to the incident light.  However, an MCU has no way of directly measuring that resistance, so a second resistor is required to form a Voltage Divider:







simulate this circuit &ndash; Schematic created using CircuitLab

As the light levels change the ratio of resistance between R1 and LDR1 changes, and thus the voltage at the point between them (GPIO in this schematic) will change.  The MCU can easily measure that voltage using an analogue input.

The choice of resistor for R1 sets the light sensitivity of the LDR, and also the range of voltages the MCU sees for different light levels.  Different LDRs have different resistance ranges, and R1 should be sized to match. You may need to experiment with different values to get the light range you desire.