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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.



Vcc/Vss
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.

RST/NMI/SBWTDIO
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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