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Posts from — June 2014

Eagle Upgrades, PCBs, and Schematic Software

Eagle PCB

I’m almost done designing a set of PCBs for one of our standard machines.  Since our customers have different safety requirements (safety controller vs safety PLC), we have to provide several different options.  So I’m doing something that seems a little unusual: the safety components (controller, light curtain, contactors, relays) are all wired to the main break out board.

At first glance, this seems like extra work: why wire to a connector which is then plugged into a board when you can wire direct?  However, it will save time (and probably money), because it allows us to have a standard base machine that we can change into different configurations in a short amount of time (my guess is 30-60 minutes) by simply unplugging the safety connectors, swapping out the safety controller/PLC, and plugging the new connectors in.

Even better, I don’t have to worry about wiring mistakes, because all the wiring is on the PCB.  (Of course, this assumes the various cables are wired correctly, but with this approach, we can wire up and test the various components in advance).

As I’ve noted, we’re using Cadsoft Eagle PCB (currently on Version 5).  However, since Eagle is running a special (get a free upgrade to Version 7 if you buy a Version 6 upgrade before V7 comes out), we’re upgrading.  I’ve found it hard discover Cadsoft’s upgrade pricing, so we had to call and ask.  The Professional Version (schematic + layout + autorouter) upgrade (V5 to V6) is $549.

I like the fact the Cadsoft does not ask for an annual maintenance contract; instead, tech support is free and upgrades are free for the major version.

Schematic Software

I was planning on getting electrical schematic software, because normally creating schematics using other tools (such as AutoCAD) is a huge waste of time, and what we had been using died a while ago.  The software I was most interested in was Radica Software’s Electra.  It’s not based on AutoCAD (a good thing in my opinion), it’s not limited (unlike most competitors),  the price is reasonable, and there’s no annual maintenance fee (instead, it’s like Eagle: free support + free upgrades until the next major version).  We don’t create that many schematics, so it’s definitely not worth it to spend a lot of money every year on schematic software.  (Note that I haven’t had time to test Electra E6 out, but I’ve seen a number of positive comments from others).

However, with these new PCBs, I’ve moved so much of the schematic into Eagle PCB, it’s really not worth it to pay for separate schematic software.  Instead, I’ll create DXF objects from Eagle, and use those in DraftSight (a free AutoCAD clone) to create the schematic.


I’m slowly creating some pages on my Trac site with useful links and info; here are a couple that might be relevant to this post:

June 25, 2014   No Comments

Preview: Cortex M4 Dev Kits


My Cortex-M4 Dev Boards

My Cortex-M4 Dev Board

Over the last year or so I’ve acquired six ARM Cortex-M4 boards; I have some experiments planed for them, and hope to be able to do some write ups this fall.  Here’s a chart highlighting some of their key specifications (of course, these boards can do a lot more, such as SPI and I2C communications).

LM4F120 LP TM4C1294 LP NucleoF401 STM32F4 Discovery Micro Python Pixy
MCU LM4F120 TM4C1294 STM32 F401RE  STM32 F407VBT6  STM32 F405RG LPC4330
MHz  80  120  84  168  168 204
SRAM  32K  256K  96K  192K  192K 264K
Flash  256K  1024K  512K  1024K  1024K 1024K
Debug  Yes  Yes  Yes  Yes  No No
USB  Yes  Yes  Yes  Yes  Yes Yes
Ethernet  No  Yes  No  No  No No
microSD  No  No  No  No  Yes No
Headers 1 Booster Pack XL  2 Booster Pack XL Arduino Uno R3 plus STM Morpho STMF4 Discovery Headers Micro Python skins (planned) None
Frame work  Energia, eLua (beta) Energia, eLua (beta) mbed eLua (beta) Micro Python Pixy vision
Open Source No No No No Yes Yes
Price $13 $20 $10 $15 $40 $59

Notes on the Chart

  • Debug means built-in debug support over USB, JTAG connector, or similar.
  • USB support varies; for example, some boards include USB OTG support.
  • eLua support is probably usable, but not very polished, on the various platforms, but that’s a guess because I haven’t tried it yet.
  • Energia is a Wiring-based IDE and framework for Launch Pads that’s very similar to Arduino.
  • Prices are approximate.
  • My apologies if the chart is hard to read; I haven’t had time to update my theme to allow for wider charts.

Stellaris LM4F120 LaunchPad (Tiva TM4C123G LaunchPad)

The LM4F120 LaunchPad is no longer available; however, the Tiva TM4C123G LaunchPad is very similar (it does have a few improvements).

I bought this board when it first come out, since TI had a special offer (around $5 IIRC).

Tiva TM4C1294 LaunchPad

I bought one of this when it first came out because I’ve been waiting for a successor to the Stellaris LM3S9Bxx MCUs (which had on-chip PHY and plenty of SRAM).  Yes, I do love to buy boards before I have time to play with them…

At EE Live! 2014 these LaunchPads were the top tool swap choice.  (At the TI tool swap, TI gives you a new TI dev board in exchange for an old, non-TI board).


I wasn’t planning on picking up one of these,  but I managed to snag a free one at EE Live! 2014 from the ST  booth.  It’s definitely a very impressive board for the price

STM32F4 Discovery

I wanted a STM32F4 board with Ethernet, and had a hard time choosing between the STM4F Discovery with Base Board (which adds Ethernet and more) or the Olimex STM32-E407 (which has Olimex UEXT connectors).  I went the STM32F4 Discovery route because it seems to have better software support.


I backed the MicroPython Kickstarter project primarily because I like the Python language (and have used it on production machines), and was curious to see how much of Python’s goodness could be packed into a MCU.  As you can see, it’s a pretty tiny board.

The base Kickstarter price was about $40; when it becomes available to all, the price will probably be a bit higher.


The Pixy is primarily a machine vision system, designed to track objects and work well with Arduinos and similar systems.  However, it could be used as a pretty powerful embedded board.

I backed the Pixy because I like machine vision (I also own 5 smart cameras), I’ve wanted to play with the NXP LPC43xx MCU at the heart of the Pixy, and because I remember the Charmed Labs guys from their Nintendo hack days.

The base Kickstart price was $59; it’s currently available on Amazon for $69.


June 23, 2014   No Comments