For this update, we successfully setup the MSP430FR6989 Launchpad evaluation board to read voltages from an analog sensor, in this case a light-dependent resistor (LDR), and display information on an LCD using SPI.

For the analog sensor, we setup a simple voltage divider circuit between the LDR and a 1 kΩ resistor. The MSP430 uses a 12-bit ADC, so the quantized value is 12 bits or 4 hexadecimal digits to save space on the display. As is seen in the video, as the hand got closer to the LDR, the measured light level decreased, and vice-versa. This test was significant because for the final project, we will be using thermistors, which are simply resistors that change resistance based on temperature, and the circuit for those will be identical to the LDR voltage divider circuit. The only real difference will be in the software, as thermistors require some additional calculations to convert the voltage to a temperature.

For the LCD, we used a graphics library to perform most of the screen rendering instructions through SPI. For this test, we simply displayed the light level value from the LDR in plain text, but this is enough to confirm the proper setup of the library and SPI commands. For the final project, we aren’t using this exact display, but rather one that’s about 0.5″ bigger. The graphics library we used for this smaller display also works with the larger display, the only difference is changing a few parameters such as screen resolution.