Yet Another PIC32 Proto Board

Over the past few months I've been doing some developments and research based on Microchip's PIC32MX 32-bits Microcontroller product line. Time to time I have the need to do some hardware and firmware verification before I commit a final design on a pcb, I'm a prototype maniac.

Searching on eBay for TQFP-100 adapters I found this one from some folks in Thailand that is not just a plain adapter. It is tailored for dsPIC, PIC24 and PIC32 parts.

What is special about this one is that it is not just an adapter, as you will see on the other pictures below, on the bottom it includes the pads for several of the support components (decoupling capacitors, VCORE caps, etc.) and a header for the ICSP (In Circuit Serial Programming) interface to get a PIC32 up and running very easily.

You can get this adapter for less than U$S 2, and taking advantage of Microchip's excellent sample program you can get free samples of several of the PIC32MX family parts. I went ahead and dropped a PIC32MX795F512L-80I/PF on it.

Some folks may feel intimidated about soldering a 0.5mm pitch100-pin surface mount chip, don't be so, as you give it a try you will find that sometimes prototyping with surface mounted components is easier, quicker, cleaner and more reliable than with the old through-hole parts. 

So how do you solder this beast ? I'll show you.

First of all, you need the right tools, patience, a good solder iron with a thin tip (I have a Weller WESD51 station with the PES51 iron and a long canonical 1/64 tip (ETS), a good set of tweezers, a pair of magnified glasses or a microscope, and more patience.

First of all make sure the board is clean, use denatured or isopropyl alcohol to remove any grease, dust, etc. Put just a tiny bit of solder in one of the corner pads, I normally do it with the lower left corner. Position the PIC32 with the right orientation, double and triple check that you put it with pin 1 where it is supposed to be, don't get confused with the orientation of the PIC32 legend on the chip, you will see it rotated clockwise 90 degrees, that's the right orientation !!

Using the tweezers or your fingers to hold the part in place making all the pins aligned with the pads, melt the solder on the corner pin so the pin gets soldered to the pad. Then add a little bit of solder on the opposite side and corner (upper left in my case, as shown on the picture). That will put the PIC32 in almost a fixed position so with your magnifying glass and/or microscope you can double check that all the pins align correctly with the pads before we move to the next step.

Then we are going to use a technique that consists on flooding all the pins with solder, that we will later clean up using a desoldering braid or wick. Do one side of the PIC32 at a time making a pause before moving to the next side so you don't overheat the PIC32.

The desoldering braid I use is a Pro Wick 1815-10F from my Texan friends of Techspray available from Mouser.


When you are done let it cool down before you start to clean each side with the desoldering braid, put the braid in parallel to the PIC32 side with enough braid to cover all the pins on that side, when you are ready put the iron on the braid (not the pins) as the braid heats up it will start sucking up all the excess solder from the pins, when you see that most of the solder has been removed remove the braid, don't let it cool down and attached to the pads or traces on the pcb. You need to be careful about not to damage the traces coming out of the pads or trying to remove the braid if some solder got it attached to the pads or traces, reheat the braid to make sure it is free of any hard connection.

Another great product I use from Techspray is a general purpose defluxer to remove all the flux left on the board by the solder. It is also available at Mouser and the product number is 1631-16S.

Once you are done removing the solder and cleaning the area you will find that you just soldered a 100-pin PIC32 microcontroller and it looks very neat !!


Now it is time to take care of the support components in the bottom of the adapter, in case you wonder about the values and what each one is for I put together a quick schematic showing how pins on this adapter are connected. Take in account that this is not a "generic" TQFP adapter, given that the Vss and Vdd pins are connected according to the dsPIC33/PIC24/PIC32 pin outs, but be aware that the Analog Vdd (AVDD) pin and VBUS pin are not connected to Vdd. After adding the bottom components and headers I added a small piece of wire connecting AVDD to VDD, without that connection your PIC32 will not startup or be recognized by your ICD or REAL-ICE.

To solder the SMD parts I normally put a little bit a solder in one of the pads for each part, then with the tweezers position the part with one hand while with the iron heating the pad with the solder. TIme ago I put together a tutorial with some pictures showing how to deal with these parts. 
You may have noticed that on the schematic I have one LED connected to RG15, looking from the bottom on the upper right you can see one of the leads of the LED soldered to the GND/Vss plane and the other which I later connected via a 330Ω limiting resistor to RG15 (Pin 1).

While I included as optional the crystal and load capacitors for it as an external source for the PIC32 main clock oscillator, I was planning just to use the internal clock. These are the particular configuration bits (for the MPLAB C32 Compiler) I used for this project:


#pragma config FPLLODIV = DIV_1, FPLLMUL = MUL_20, FPLLIDIV = DIV_2
#pragma config FWDTEN = OFF, FCKSM = CSECME, FPBDIV = DIV_1
#pragma config OSCIOFNC = ON, POSCMOD = OFF, FSOSCEN = OFF, FNOSC = FRCPLL
#pragma config CP = OFF, BWP = OFF, PWP = OFF

After finishing with the components on the bottom, adding the wire for AVDD and the status LED, I added the headers for each side and for the ICSP interface. Created a simple program to initialize the PIC32 and get the LED on RG15 blinking, applied power and voila the thing became alive !!

I've several other development boards and gadgets for development with the PIC32MX family, but I really like this simple one that has nothing besides the minimal support components and one LED connected to its pins.

Hope you find this article useful for your PIC32 projects, don't be afraid of soldering a TQFP-100, the worst that can happen is you get a wasted free sample and few bucks on parts.

Happy Prototyping !!

Cheers

Jorge

chipKIT PIC32MX based boards by Microchip and Digilent

Well, after some anxious waiting the new chipKIT™ development boards finally arrived this week. I'm obviously talking about the chipKIT™ Uno32™ and the chipKIT™ Max232™ boards produced by Digilent and co-developed with Microchip.
First of all notice that chipKIT™ is a registered Trademark by Microchip Technology, Inc. (they seem to be very cautious to include the ™ everywhere.)


These boards feature Microchip's PIC32MX 32-bit microcontroller family and claim to be somehow "the first 32-bit microcontroller-based platforms that are compatible with existing Arduino™ hardware and software" (more about the compatibility thing later).


The boards are produced by Digilent, Inc., and they share the same high quality and detail I've seen on other development boards produced by them. No need to say that the new chipKIT™ platform has behind it the marketing machinery of Microchip, and that the development of this new platform seems to have been originated within the Academic Exchange group to meet the demand for a 32-bit solution requested by the hobbyist, academia and embedded engineering communities.


(Hey look !! Microchip even produced and uploaded a video on YouTube.)
Update: For some reason the original video has been removed from YouTube.


As you may probably know "Arduino™ is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software", and until now all Arduino™ hardware has been based on Atmel 8-bit microcontrollers.


Hmmm "open-source", that's sort of new territory for Microchip, and obviously generated some buzz when the first rumors about these boards hit the development community, where Microchip licensing terms for most of the "License Free" stuff they make available for download and use are very well known for not allowing you to share or redistribute any changes or contributions to their stuff, kind of totally opposed to the spirit of the Arduino community.


Ian Lesnet from Dangerous Prototypes had a great initiative to collect questions from the community to be asked during a phone interview with the people involved in the chipKIT™ platform development. Ian was very kind to make the recording of the interview available on-line, you can find the recording and an interesting exchange of comments on this thread of Dangerous Prototype's forum.


OK, how compatible are the new boards with the existing Arduino™ stuff ?.


First of all notice that we are talking about a completely different Microcontroller, that means you need a different compiler and integrate it with the development environment. What Microchip did ? (something they not let you do with their stuff) took the open-source Arduino™ IDE and modified it to include support for the PIC32MX and redistributed it renamed as MPIDE (for Multi Platform IDE) with what seems to be an open-source license.


The key question is if the existing Arduino™ libraries will fully work on the new platform and if Microchip adds new libraries to support the new features introduced by using the PIC32MX will also be open-source and freely modifiable and distributable.


There are some folks already testing how well the existing libraries work and doing some performance testing as related on this article at Hack a Day, and some pin compatibility analysis by the Rugged Circuits folks.


About the hardware, the fine letter says "footprint compatible", and the intention here is to have the same form factor and approximate pinout so you may be able to use many of the already existing Arduino™ shields, but keep in mind the the chipKIT™ boards are 3.3V and there may be some shields that require 5V, remember always to check the schematics and documentation of each particular shield to avoid the unpleasant blue smoke.


Now taking a quick look at the new boards, this is a quick and preliminary first look at them, I'll post more articles as I power them and start doing some developments and tests.


The chipKIT™ Uno32™

Inspired and "footprint compatible" with the Arduino™ UNO. It features a 64-pin PIC32MX320F128H 32-bit Microchip microcontroller with 128KB of internal FLASH program memory and 16KB RAM, instead of a Type-B as the original Arduino™ UNO it has a mini-USB connector for the serial interface to the FTDI USB-Serial converter.


One thing that bugs me being one of the nice features of the PIC32MX family that you can have a nice chunk of program memory, why for one more dollar they didn't populate the Uno32™ with a PIC32MXF340F512H that has 512KB of FLASH and 32KB of RAM? It will probably be the first mod on my board.




The chipKIT™ Max32™

Inspired and "footprint compatible" with the Arduino™ Mega2560. It features a 100-pin PIC32MX795F512L 32-bit Microchip microcontroller with 512KB of internal FLASH program memory and 128KB RAM.


One nice feature of this member of the PIC32MX family is that it includes an 10/100 Ethernet MAC module, it requires and external PHY chip for a 10/100BaseTX but Digilent said to expect an shield that will take advantage of the Ethernet and USB interfaces by July.






Both boards include direct access to the PIC32MX ICSP interface in case you need to program the PIC32MX directly. The boards are preprogrammed with a bootloader and the classic flashing LED demo. In case you wonder why the ICSP header pins are not in line read this tutorial article from SparkFun.


One nice change on the layout of the new boards is the position of the RESET button, as you can see on the pictures if you have a shield installed on top of the Arduino™ boards unless you have a hole on the shield it is almost impossible to hit the RESET button, the new chipKIT™ boards have it in one of the corners where even with a shield on top it makes the button accessible from the side.


I'll start playing with the boards and post additional articles. As Microchip, I took care to include the stinking TM mark on all references which they make explicitly clear that are trademarks of Microchip and just saying that other trademarks are from their respective holders blah blah blah without mentioning that Arduino™ is a registered trademark of the Arduino team.


Hope this incursion of Microchip in this arena brings a change of attitude and helps they learn from this experience and embrace some of the practices of the open-source community.


BTW, even when it is a registered trademark the boards and associated software are not "official" Microchip products so don't expect direct support from Microchip, if you need help visit the chipKIT Forum (how original !! they also registered the chipKIT.cc domain, well it goes in companion with the originality of the packaging too).


Some links to keep handy:

• chipKIT Forum
• Microchip official chipKIT page
• Digilent Product pages
• MPIDE and other software download page

You can currently purchase the boars via Digilent or Microchip Direct, I'm sure there will be other distributors in the near future.


Looking forward to see the first batch of clones :-), hey it is open-source after all !!


Cheers
Jorge