MSP430 PCB Considerations

Anas Imtiaz said:

There are a number of 0R resistors - what are they for? Do I need to put those on my board?

0R resistors are usually soldered jumpers. Used to connect two wires for one setup, but leave them separate for another, without need to place a through-hole jumper on the PCB.

I guess, many of them could be replaced by a 'solder-jumper'two half-moon copper pads that can be connected with a drop of lead. THis was the commen way back in times before SMD parts and sophisticated layout software. The problem is, if the default state is 'closed', todays layout programs (especially the often used Eagle) do not have a way to have the element be connected with copper, but both sides have different signals.
(I solved this in my projects by introducing additional top/bottom copper layers that contain such kind of bridges - these layers also take surplus copper heat spreaders that belong to a device etc.)

Anas Imtiaz said:

Many capacitors and some resistors have DNP written next to it. They are on the target board too, again what does that mean and do I need them?

"DNP" IMHO means "Do Not Populate". So no, you don't need them normally then.

Anas Imtiaz said:

What is the purpose of capacitors placed between Vcc and Gnd? (are they 'filter capacitors'?)

Yes. It depends on where they ar eplaced. They may only are blockign caps to keep ripple currents from the supply line, but may also be low-pass filters (e.g. if you have a series resistor between DVCC and AVCC and a cap from AVCC to AVSS, then is it a low-pass, further filtering the AVCC supply). Or may be storage capacitors, e.g. on the VCore pin to DVSS.

Even if the chip has morte than VCC and tehy are internally connected, the largest capacitor is needed on the pin that is connected to VCC while the others are just buffers'. if all are conencted to VCC separately, the pin that is nearest on die to the highest current consumption or the strongest curretn ripple requires the biggest capacitor. However, the design guides tell that you can also just populate one with the total capacitance. The differences are small. It gives you some freedom in layout, since smaller caps are usually - smaller.

Anas Imtiaz said:

what is the minimum set of components I need on the board to get it running

A blocking capacitor between VCC and GND should be there. Else the processor could get unstable when you so somethign that suddenly causes a high load. Remember, on high frequencies, even the VCC supply line behaves like an inductor, limiting the current.
Then there is the capaciton on VCore (if present). it is a must.
A pullup resistor (47k) and a capacitor to GND should be on the RST pin for proper startup on a slowly rising supply. I think that's all what you really need.

 

Anas Imtiaz said:

1) There are a number of 0R resistors - what are they for? Do I need to put those on my board?

Sometimes 0R resistors are used to ease the routing or reduce the the number of layers needed as you can route a signal under a 0R resistor (if big enough) and thus effectively cross another signal line.