History Museum

Skill Level: Intermediate

by Nate January 07, 2007 | 7 comments

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Clearing out various  boxes here at SparkFun Electronics, we come across piles of old prototypes. You  may ask, what's a prototype? It's a design that we, the engineers, screwed up. May we  bestow upon you a few rules to laying out a PCB. In order of importance:

   
1. Print off a 1 to 1 and check the footprints for each part
   
2. Don't forget the standoff holes
   
3. Double check that TX and RX are connected to RX and TX of the two devices
   
4. Put the date on the board either in a copper layer (preferred) or on the    silk screen layer (silkscreen can flake off after a few years)
   
5. Be sure that the board has silkscreen indicators at least on the pins, and    hopefully a board revision!

Now if you don't believe these rules, here's 61 reasons why the above rules  apply. We've got piles and drawers full of mistakes (also known as drink  'coasters').

A few more words of wisdom:

   
• We don't actually use part indicators (R1, R2, C13, etc) on many of our    tightly packed boards. The assembler/engineer can always refer to the layout    files. It's more important to label the connection pins. Once the board has    been populated, you will need to know where 'VCC' and 'GND' are more often    that needing to know where Q7 is located.
   
• Try to indicate the part dimensions with the silkscreen layer. This will    help prevent larger parts from hitting smaller parts during the layout process    and eventual build.

The follow pages are a select collection of designs produced by SFE. Sorry if it makes  your head spin. May you learn something from our many, many mistakes.

   
• Page 1 - The general collection
   
• Page 2 - The development cycle that started SparkFun Electronics
   
• Page 3 - The epic progression of the BlueSMiRF

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First we will start with the general pile and move to the more  interesting design progressions.

Cluster .... This is a proto for the  ringer board in the  Port-O-Rotary phone. List of problems : Base/Emitter were swapped on the  transistors within the h-bridge. That was a fun fix. The drill holes for the  large diode in the corner were very tight. You may have the  dimensions/layout on your part correct, but for larger current/voltage parts,  double check the drill holes.

Proto backpack of the SerLCD product for both standard SIP  type LCDs and dual row connector LCDs. Very old. Never populated. Seen as having  too many options, never got the firmware ironed out, and the SIP type LCD is a  bit more common than the dual-row type LCD connection so we never really went  with the idea.

Original prototype for the CP210x breakout board. The switch was wired completely wrong. It was a  schematic component mistake. Looks like there was also a VCC net disconnect. At  least we got the mounting holes on there...

This was the very first design we panelized. SerLCD v2 with SMD parts! Looks great, yeah? Except that when we first  started with the stenciling  and hand populating, we didn't realize that a human would have a very  difficult time placing the components in the center of such a large panel. Live  and learn. We didn't know this DFM (design for manufacture) error until the PCBs  arrived and we tried to populate it. Ever after this 1st board, we kept our  panelized designs small enough that a human could place components in the center  of the board without too much problem.

SerAccels in various versions. We've been through a lot of revisions.  Here are a few. There were probably 15 more revisions. Shaker v1 was a proto  that never got populated. It was an accelerometer with PIC and nRF2401 circuit  and wire antenna. This is a pre-cursor to the WiTilt. Notice the branding and migration from 1206 to 0603 sized parts. The  ICSP (In Circuit Serial Programming) header also shrunk in size over time. The  part indicators eventually went away.

Wow. This is an old one. Here we have a proto for two? ADXL  accelerometers and a PIC with a connection of an RF-24G wireless module. This  pre-dates the nRF2401 circuits. Ran off a 20mm coin cell, or at least that was  the plan...

The multiple drill hits (awkward hole in the board) is where  we experimented with a vertically oriented ADXL chip. Never really worked out.  We got the board rev (v01, v02) on there as well as the date. Go us. Never  populated.

Ahh yes. The SMEEPROM. Serial Miniature Electronically  Erasable Programmable Read Only Memory. The name was just wrong from the  beginning and is still very bad. This design was to use a Smart Media socket and  a PIC to allow the user to serially record data to a Smart Media card. Not only  was the footprint for the Smart Media socket nearly impossible to layout, the  PIC (16F872) was far too inadequate to handle the FAT16 routines. Great idea,  but then SD  cards (Secure Digital) came along and replaced the Smart Media technology.  Thank goodness.

Here we have a panel of designs that never made it out of  'shearing' phase. We used to get panels of different designs (to save money) and  then shear them apart with a large metal shear. Not fun.

Nuther panel. Who needs a frisbee?

This is the first of a few 'progressions' showing the  different versions. From left to right in time, the left most design was the  first version.

This board was to be a motor driver board for a project  nick-name 'SparkFun Toys'. Different boards would stack on top of each other  gaining power and communication from the metal stand-offs.

The Toys project was really to create a robot for the 8-15  year old market. A robot that the child could assemble without soldering and be  able to tweak. We came close but then decided that we really didn't have the  resources or market leverage (think Radio Shack) to pull it off.

This was the 3rd rev and we still messed up the footprint on  this small h-bridge IC. Here we have a voltage regulator, PIC, and h-bridge  driver.

Here is another progression of another board for the same Kit  bot project. This used IR sensors to detect other bots. Never firmware  completed. The idea was that Power, Ground, TX, and RX would be connect the the  4 screw stand-offs between boards. Less connectors this way! Easy to assemble!  There would be a master 'brain' board screw to various sub (or slave) boards.  Good idea. No resources to pull it off. Lots of prototypes though.

This was a test board for NiMH battery charging. Never  populated, but imagine how much time it took just in schematic and layout.

Old, old, protos of a graphical Serial LCD board. A test bed  to test the serial LCD boards (never worked) and a NiMH charger board with SMD  regulator instead of the PTH regulator version.

This is a collection of boards to work on Mazer. Mazer was a  robot entered into the 2005 Robothon  Line Maze competition. It eventually won 3rd! The bottom left board was an  attempt at creating our own H-Bridge. Not a trivial task. We eventually left it  up to the professionals (TI and the trusty SN754410) as seen on the Mazer v1 board. The other boards titled 'Mazer Eye'  are the infrared sensor arrays to detect the black line in the maze. Little did  we know that the IR light emitted from each sensor would splash into the other  sensors so I ended up using some short pieces of heat shrink to form a dark-hood  around the in-between sensors.

Ugh. These are very early prototypes of the  Uber board. These  boards use a PIC to talk to a GPS unit (Lassen  iQ or UV40), a cellular module (GM862),  an SD card socket, an ADXL  accelerometer, and a CP210x USB to RS232 IC. Very old design. You can see rev 2 had cut-outs for  various antennas and wiring. It was a wild design that eventually lead to the  Uber board. It's always difficult to stop revising a design, because there is  always newer and better technology. At the time of writing, the GM862 now comes  in a GPS flavor that removes the need for the extra GPS module. The SD socket  has changed, and with DOSonCHIP, any micro can record data to FAT files. The  CP210x USB to RS232 IC has improved to the FTDI  FT232RL IC or even the USB Mass  Storage protocol on a LPC2148. And the ADXL has grown to tri-axis of the  ADXL330. Technology moves fast!

This is an old PIC-P18 dev board that was used to communicate with a GPS rover as a student  senior project. This board received serial commands from a computer. The  computer had a wireless video link to the GPS rover and was running image analysis (looking  for an orange traffic cone). The rover had a GPS unit  on board (the old UV40). The computer would send motor control commands to this  board. This board would then transmit a PWM (right and left motors) over the cheap-o wireless links at 315MHz to the Rover. The Rover would drive  accordingly and report back GPS coordinates (received over a cheap-o 434MHz link). The computer would tell the rover to drive to a given  set of long/lat coordinates and get within 10m radius with GPS. The computer  would then steer the rover towards the orange cone using image analysis. I say  the rover 'would' and 'did', but the system didn't really work on demo day. The  only thing the computer 'did' was come close to driving the rover off the roof  of the engineering center at Univ. of Colorado. Anyway, the PIC-P18 board with the PIC 16F88 and Bloader  is a great way to quickly prototype and get a simple proof-of-concept device up  and running.

The original Wall Clock  controller complete with blown voltage regulator and GPS unit. Notice the  footprint for the RJ45 connectors was reversed. Luckily, the connectors could be  mounted to the bottom of the PCB without modification of the PCB - however the  cable wiring had to be reversed to match. Always, always print out your 1:1 PCB  and compare parts to holes. Or don't check it (like us) and have stacks of dead  PCBs.

Another time warp. This is the  Wireless Weather Station  Bulletin Board System main PCB. This board gather data from various weather  sensors and posted that data across a GM862 cellular link. We used a solar cell to charge an SLA (sealed lead acid) battery. What did we learn  from this PCB?

   
1.    

   Not all 2N3904 NPN transistors are wired the same. Always check  the pinout of the device in hand against your footprint.

      
   
2.    

   When dealing with PCBs that have been sheared by hand there is a  strong chance that you will not perfectly cut along the intended board outline.  In this case, we had this really horrible power short when connecting a DB9  cable (for programming and debugging). The cause? Notice how the DB9 connector  lines up with the edge of the PCB. The copper pour on the top of the PCB is VCC  and was exposed ever so slightly when we sheared into the edge of the board.  When the serial cable was attached, the DB9 connector would flex slight downward  under the weight. The metal face place (which is grounded) would touch the  slight exposed VCC plane causing the power supply to short out. Jeebus that was  a freaky bug to hunt down.

      
   
3.    

   The button footprint was reversed so we had to shoe-horn the  button, side-ways.

      

Signal disconnected on the WeBBS board. So common with proto  PCBs. Laying out a PCB is tricky, but making a faulty PCB work is an art form.

This was a rather large PCB intended to show various  high-speed digital design problems including clock delay, metastability, cross  talk, and ground plane bounce. It, ah, sort of worked.

This was the first programmer before there was a SparkFun  business! When playing with bare PCBs, make sure you don't have bits of wire or  tools in your work area. Setting this programmer down, sparks ensued, a $120  programmer (bought off ebay) was blown, and a business (the 'SparkFun' of Spark  Fun Electronics) was created. One of the voltage regulators was fried. Newfound  Electronics is still kicking I believe, but they don't seem to be making this programmer  anymore.

Progression of the GPS eval boards. There are about 12 revs  not shown. On the left we see the  really old UV40/TF30 USB breakout board (one of the first original SFE designs).  2nd, we have an example of what happens when you think your design is ready for  production, before you actually run a prototype. TX and RX were accidentally  swapped and a stack of PCBs were scrapped. Next is the RS232 UV40 board. Worked  great until the UV40 GPS module was discontinued. On the right is the first  proto of the popular Lassen iQ RS232 eval board.

   
• Page 1 - The general collection
   
• Page 2 - The development cycle that started SparkFun Electronics
   
• Page 3 - The epic progression of the BlueSMiRF

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This constitutes a small portion of the hard work we put in  here at SparkFun Electronics. Thanks for checking us out! Please use this  information at your own risk.

January 7th 2007

Congrats! You've made it to page two. If you've thought about  creating your own product, let us give you a tour of our own product  development. It spans 5 years.

A little history to SparkFun Electronics... This pile of  boards was a product developed for the sport of rowing (the sport of choice by  the SFE originator - Nathan Seidle). This was the device that spawned SFE. We  started from scratch and designed a few revisions of this rowing amplifier (mind  you, we were in college and knew nothing about PCB layout or embedded  electronics). Then, because the programmer blew out, we needed to buy a new  programmer. Olimex kept coming up on  internet searches, and because the  distributors of the Olimex products had such bad websites at the time (no online  checkout, no images, etc), Nathan thought he  could do better. He created the original SparkFun Electronics website to sell  the various tools that he need for the amplifier product development. The Spark  Fun sales and site development grew to a full time job over the following two years and, as  they say, the rest is history. SparkFun Electronics became it's own beast. But  back to the product development...

Good old wire-wrap prototyping with a PIC 16F876 with a  pre-packaged backlight driver. The graphical screen and touchscreen come on an old dev board hand assembled  from CrystalFontz. Not too bad for just starting out. This  was around July of 2002.

The first PCB layout in September of 2002. This predates the  creation of SparkFun Electronics by three months.

This is the only hand etched PCB by SFE. This was enough.  Everything after that was professionally fabbed.

Here was have the 'v01' progression of this product from left  to right in time. Starting with 2-24-03 on the left and 7-12-05 on the right.  Two and a half years of work and the design was eventually scrapped and started  anew with a beefier processor and parts. It's a constant learning process.

2-24-06. All sorts of fun. No stand-off holes! Notice the  power resistor hanging off the side. The drill holes where too small. I don't  think the LCD ever worked on this layout.

Notice the original  CFAX 50-pin tab connector, hand soldered.  The tab to the LCD is plastic so it would melt while soldering it to the PCB.  Ugly, but it taught me how to hand solder!

7-3-03. Bigger processor (16F877A). Added an ADXL311  accelerometer. Serial connection, and all sorts of goodies.

7-29-03. New mixed layout with corrections. Never populated.

8-18-03. More goodies. This board uses the new audio amplifier  with heat conductive adhesive with stuck-on heat sink. Crazy. Bad voltage  regulator footprints. The backlight circuit worked though!

You thought you had it rough. That's the 50-pin tab connector  hand soldered. It worked! But only once. This was the old style CFAX connector.

The same board with  screen folded down into place.

Next rev dated 5-12-04. All sorts of problems, but reset  button, new v-regulator and external 32kHz RTC crystal.

7-2-04 revision. Never populated. Notice the bad silkscreen  outline on Y1 crystal. This was coming dangerously close to the 22pF caps.

7-12-05. Eventual alpha release unit featuring the Lassen iQ,  newer 18-pin  CFAX connector (ZIF connector was much easier to solder), charging  circuit with heat-sinked voltage regulator, power resistor, et al. Large  10,000uF cap was to help reduce interference from the EL (electroluminescent)  backlight and the audio amplifier. As much work and time went into this layout,  it was eventually scrapped after three years of work for a better, more powerful  unit. Product development is painful, slow, and very expensive.

Page three - the progression of the SMiRF (Serial Miniature RF  device). The SMiRF started in June of 2004 when the 2.4GHz transceiver module  was successfully used to transmit data from one module to another.

These modules are very flexible and powerful, but the amount of  firmware to get a link up and running is daunting to the first time user. Many  users simply needed to move serial data from point A to B. This could be done,  but it required an separate microcontroller to receive incoming serial  bytes and handle the protocol interactions with this module. Our goal was to  make a 'black-box' product. The user shouldn't care how the data gets there, all  they needed was a way to send serial strings over a wireless connection.

The very first proto was two RF-24Gs in a breadboard with two  16F88s. Once the idea was proven, we used the bare-bones PCB  service from Advanced Circuits. You can see those boards on the left.

There was all sorts of problems with layout, but this was also  the very first time we had soldered such tight pitch components. This  board uses the CP2102 (it was the CP2101 at the time). The first time we attached this  board to USB it was shear terror. The first time the board actually enumerated  and a Virtual Com Port, it was shear euphoria. Once you solder a leadless, tight  pitch IC like this, and get it working, all other assemblies begin to look easy  - at that eventually became a problem! (More below)

Here we have 'v02' in 7-28-04. Notice the footprint for the  RF-24G is flipped around the wrong way. Ugh. You can also see the internals of  the RF-24G module with the shield removed. That looks like a QFN like the CP2102.  That means we could possibly solder that ourselves...

More testing 8-10-04. The board could be populated to become  either a 4-pin serial device or it could populated with a USB connector and  CP2102 to become the 'base' unit. Because the parts were on both sides of the  board, each unit had to be hand soldered. I believe we ended up selling a few  pairs on units with this external module/backpack design.

The next step was obviously to incorporate the Nordic IC and  circuitry onto the same board. This board was our first attempt at soldering the  nRF2401 and surrounding 0603 components. It was poorly laid out (for 2.4GHz  freq!) and used a rather large 16MHz crystal, and QFN packaged 16F88. This  device was to use a Nordic RF circuitry, and PIC, to wirelessly transmit  accelerometer data. We  used this board to prove the nRF circuitry as well  as develop a new product. Notice the lack of antenna - there was supposed to be  a piece of wire-wrap-wire that would be soldered onto the board near C11. Much  to our surprise, the board worked! We were able to actually get this thing to  talk to our original module-based SMiRF. Excellent! The board emitted enough RF  noise that it probably wouldn't pass FCC testing. Range was limited to about a  meter, but it worked!

So we quickly rev'd the board to include a power switch (what  a crazy idea), status LED (handy), PCB trace antenna, and a smaller and much  cheaper 16MHz resonator. The board didn't work. So we trouble shot the board,  checked the connections, re-checked, re-programmed, nothing. So we built a  second board - tediously checking everything. Nothing. This was a painful lesson  on the difference between a resonator and a crystal. The Nordic IC requires  16MHz clock source to operate. The clock needs to be within 20ppm (parts per  million) so that two units can understand each other at 2.45GHz. This is a  pretty tight tolerance, but obviously needed for such high frequency  communication. A resonator is a piece of ceramic cut in such a way that it  shakes or 'resonates' at a given frequency. The process is much cheaper than the  equivalent quartz crystal process. However, where the quartz crystal can be  created with 20ppm tolerance, a resonator can only achieve +/-0.5%. 20ppm is  +/-0.00002%. Ahah! The board is functioning just fine, but the 16MHz resonator  is so sloppy, no two Nordic circuits can talk to each other. AHHHH.

So a quick retro-fit of the original 16MHz quartz crystal and  the board came to life. What a great sanity check that was. So this proto taught  us that the nRF circuitry would work, the PCB antenna worked well enough  (limited but ok range of 10-15 meters), and we would need to find a suitable 16MHz SMD crystal  that was smaller, and slimmer in height.

And here is the eventual super slim design. Date your boards -  we forgot to. This design was fabbed around 9-15-04. This is a rather small  design constituting an accelerometer, controller, battery, and RF link. Sound  familiar? This is basically a foot-pod like the Nike+iPod thing or the  ANT based Garmin Forerunner.

Here was the collection of boards that got trashed because of  the faulty resonator design.

Here are the protos for the SMiRF with etched antenna. We  found that this lump-node antenna didn't help our reception range so we resorted  back to the trace antenna. The boards did work however! Sometimes I really miss  the days of shiny leaded solder...

The 'final' rev. Here you can see the USB populated board with  stub trace antenna using a larger 16F688 PIC (and a small jumper wire fix).  Worked well enough, but the firmware was always a problem. You really couldn't  push the data rate past 9600bps and the system would drop packets if the range  was any more than 20-30 feet. This was a hassle. Around this time we started  experimenting with the Bluetooth module from Mitsumi.

This  Bluetooth module was a pre-packaged solution to our  serial cable replacement problem. It was everything the SMiRF was trying to be,  just with a whole team of Mitsumi engineers behind it. The cost of this module  is much higher than the part costs of the Nordic solution, but when the  development cost was weighed against the low-purchase volumes, we decided to  abandon the fun SMiRF and created the  BlueSMiRF based on this technology. Works  great!

   
• Page 1 - The general collection
   
• Page 2 - The development cycle that started SparkFun Electronics
   
• Page 3 - The epic progression of the BlueSMiRF

---

This constitutes a small portion of the hard work we put in  here at SparkFun Electronics. Thanks for checking us out! Please use this  information at your own risk.

January 7th 2007