Basic concepts PCB building and dsPIC

[Electron_23]

Hello,

I am a student of electronics engineering and this year I have been asked to develop a Micromouse/maze solver. For that I will use a dsPIC33E controller, two voltage regulators to 5V and 3V3, a dual motor driver, two magnetic encoders, and some sensors. My question is pretty simple, because my problem is that I have never built a PCB so I do not really know the process. The questions are:

- Do I have to design it in Eagle, make the PCB manufactured without the components, and solder they by myself? Or when you order it to the manufacturer you also give them the components and they solder it?
- For the dsPIC33, what do I have to connect in the schematic apart from the components I mentioned above? I mean, I guess there has to be some pins for programming or communication with the computer when programming, right?

Sorry for these basic questions but I am not familiar at all with this kind of things.

Thank you very much.

-Electron_23.

 

[KrisBlueNZ]

Hello and welcome to Electronics Point

A PCB manufacturer will send you a bare PCB. You can send it to another company to get the components installed, but that's only economical for large-quantity runs. So you'll need to source and install the components yourself.

Yes, your board will need to have some kind of connector for "in-circuit serial programming" ("ICSP") to program and reprogram the dsPIC. For the PIC series, these have 5 or 6 pins. You will also need a programming interface from your computer to the connector, such as a PICkit 2 or PICkit 3. You may want to modify your programming interface or make an adapter so you can use a more compact connector, so you can save space on your circuit board.

This information is on the Microchip web site (http://www.microchip.com) and in the data sheet for the dsPIC device.

Please feel free to ask any other questions here. We have several people here with PIC experience. The Microchip web site also has forums which may be helpful.

 

[pyromaniac4382]

I think if this is a one off project that you will be hard pressed to find a cheap method for a PCB to be manufactured and assembled with the components you choose. So your best bet is to design your schematic and board layout within whichever CAD software you use based off the components you purchase/purchased from a supplier, and them solder the components on yourself. There are a bunch of PCB manufacturers online. I have had luck with iteadstudio ($40 shipping included for 10 boards at 10cm by 10cm) and OSHPark (3 boards for $5 per sq. inch + a shipping cost)

If this is your first time I would recommend through hole components for less tedious mounting. That brings me to my next point, if you are using only through-hole components maybe you should consider perf-board?

 

[chopnhack]

Also check http://www.expresspcb.com/ - they have some interesting information under tips for PCB design and resources for engineers. I agree that perf board should be your first experience with making circuits, but your circuit may have quite a few connections, it might get "busy" on the back side with a lot of wires. A PCB will look very professional. Best luck any which way you go and please post some completed pics!

Just checked out DesignSpark: looks very good - http://www.rs-online.com/designspark/electronics/eng/page/designspark-pcb-home-page also free

 

[kpatz]

- For the dsPIC33, what do I have to connect in the schematic apart from the components I mentioned above? I mean, I guess there has to be some pins for programming or communication with the computer when programming, right?

Study the datasheet, especially the parts about what connections are required. In addition to an ICSP header to connect a programmer, many PICs have multiple Vdd and Vss pins that have to be connected to the power rails (and if multiple Vdd and Vss pins are provided, they all should be connected), possibly an analog Vdd pin that requires power and a ground that's somewhat isolated from the digital ground, and decoupling capacitors (0.1uf ceramic) are essential on every power pin. If the chip has an on-board regulator, there may be additional capacitors required. A larger "tank" capacitor near the PIC on the power rails is helpful too. A 10uf electrolytic will work for that. If you're using a crystal or resonator to clock the PIC, you'll need to place that as close to the OSC pins as possible, and there are load capacitors needed for most crystals. It'll all be explained in the datasheet.

Decoupling capacitors are essential for every digital IC on the board, not just the PIC. Put them as close as possible to the power (Vdd/Vcc) pins. Consider using a ground plane when designing your PCB, it'll make things easier for the most part.

Unused I/O pins can be left unconnected IF they are programmed as outputs in the firmware. Leaving inputs floating can cause all sorts of issues, so if there are input-only pins you aren't using, they should be connected to either Vdd or Vss. If you're making a PCB, add resistors to these pins so if you need to use one down the road, you can simply remove the resistor and add a jumper to wire the pin to something else.