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Program a MSP430 microcontroller pt. 2

Filed Under: geek it yourself, electronics

Basic Connections
Before we program the MSP430, let's look at the basic connections required to get it running.

As with any chip, connect every power and ground pin. Manufacturers use different terms for these. Other names for Vcc include: Vdd, power, supply, "+", the bumpy side of the battery, and the red wire. Vss is "ground", and almost always 0 volts. You'll also see ground referred to as: negative, ground, "-", gnd, the flat side of the battery, and the black wire. Decouple each pair of supply pins with a 0.1uF capacitor (C1). These small value capacitors prevent electrical noise from running rampant in our circuit.

In this lot, we're just interested in the RST function. A circuit tends to be a bit noisy when power is first applied. The RST pin and resistor hold the MSP430 in a reset state until the supply is adequate for operation. The RST pin also resets the MSP430 if there is a brown-out, or unacceptable but temporary reduction in supply voltage. This pin gets a 47K ohm resistor (R1) to the power supply. This is very similar to the MCLR pin on a PIC microcontroller.

Optional features: 32.768khz crystal
The MSP430 has a really cool function: most newer models have built-in capacitors to support a 32.768khz time keeping crystal used to implement a real-time-clock. The diagram below compares the stuff you need to keep time on a MSP430 (Q1) and a PIC (Q1, C1, C2). This is a huge time saver because routing a clean ground supply for external capacitors (C1 & C2) can be a pain. Even better - the value of the internal capacitors can be adjusted from software! This isn't strictly required to get an MSP430 up and running, but it's a great feature. Learn more about routing the MSP430 crystal in this PDF.

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