In this episode I will be repairing my AVR ISP MKII programmer by replacing the on-board boost converter (TPS61020) and I will also upgrade the 6 pin ISP programming cable to 1m length.

A while ago, Francesca from Element 14 kindly contacted me to ask if I wanted to receive some products from their catalog for review. I said yes and since I already had a wishlist going on (as most electronics guys have) it was easy to pick up some products. I also considered current and future projects when picking the items and so I had 4 items:

I asked for the STM32VLDISCOVERY because I wanted to play with one of these ever since I discovered this STM32 book written by Geoffrey Brown. The book seems so nicely written and from a practical point of view seems like it will get me started and working on the STM32 in no time. I’m also working on a couple of projects right now for which the STM32 might seem like overkill but I might use it anyway just build some experience around this chip.

I asked for the ATXMEGAA3BU-XPLD because it is a nice platform all around. The MCU is the ATxmega256A3BU and you also get some analog sensors, an lcd display and lots of IO’s. Excellent for when you need to throw something together and test it on an Atmel ATXmega. The ATSAM4L-XPRO which I received in error, features Atmel’s ATSAM4LC4C Cortex-M4 MCU which is nonetheless interesting in the industry but isn’t of much use to me on it’s own without some expansion board.

The TPS54231EVM-372 and TPS5450EVM-254 from Texas Instruments were requested because I use both of these in two of my projects and I wanted to have a reference testing platform for comparison to my own implementation in layout and design. I use the TPS54231 in the new Audio Spectrum Analyzer to power the digital/LED section and I use the TPS5450 in my DIY digital power supply as the switching  pre-regulator before going into a linear reg.

More will follow on these as I am going to perform some measurements like output noise on the TPS54231EVM-372 and TPS5450EVM-254 using my entry level scope and compare the results with the ones from the datasheet.

Also if you would like to checkout more products from these manufacturers, see the Newark category pages:

itead studio pcb

I recently had a batch of 10 pcb’s for an ongoing project fabricated with iteadstudio pcb prototyping service. They guarantee 100% electrical test on their product page. One month later I receive the pcb’s and decided to watch them under a microscope for inspection. I wasn’t particularly checking for the e-test, I was more interested in seeing if the small pads and vias  look good. I was however surprised when I did not find the small marks on each pad which are a good indicator if the e-test has been performed or not.

From my knowledge in low volume production e-test is being made with a flying-probe type machine and as the name suggests the flying probes would leave small marks in each pad where they touched to make electrical contact. In my case as it can be seen in the picture above the pads show no marks so I suspect itead is lying about their 100% e-test. I checked all 10 pcb’s that I received and none had the marks that an e-test would leave behind. They were however all marked with a stripe on the edge as it is usually the case with pcb’s that have been e-tested just as a reference to differentiate tested from non-tested pcb’s.

My guess is that they are trying to lower their cost of production by visually inspecting small pcb’s instead of passing them through a real e-test which would cost money and would take time to setup.

I reached out to iteadstudio and asked if the black line marked on the edge of the PCB’s means they’ve been tested electrically although the meaning of the line has no significance since the product is advertised as 100% e-test.

I found this reference on DagerousPrototypes Forum , other users also report the pcb’s don’t have scratch marks on the pads. Another user reports he found electrical problems on pcb’s from itead(and they should be 100% e-tested).

On their website there is this article where they explain how they handle the pcb business; at 0:10 there is a picture with a machine they say its for e-testing the PCBs. That doesn’t look like a flying probe machine, maybe its a nail bed. Anyway the pcb is already finished when they test it and should have scratch marks afterwards, this rules out the possibility where they test the pcb’s before applying the finish. The nail bed is also not a good option as it would take too much time to setup something like that for each pcb they sell.

And itead replied…

Dear Florin C.

All of the pcb’s have a stripe on the edge,it does not mean they have all been electrically tested ,it is the same as outline .

Sincerely Yours


I probably did not explain clear enough that the line I’m talking is hand draw on the pcb side with a black marker so the guy is saying something about the board outline. But that is not so important when you read the part where “it does not mean they have all been electrically tested”. I wonder how is this possible for a product that is supposed to be 100% e-tested.

My conclusion is that you’re better with seeed’s pcb prototyping service with 50% e-test. Users are reporting that half of the pcb’s actually have marks and they’ve been tested.

October 5th, 2011

7400 Logic Competition

Youritronics is a proud sponsor of the 7400 Logic Competition. We are giving away:

If you have a project based on 74XX logic circuits you should register for the competition. There’s about 3 weeks left before judging begins on October 21, still plenty of time for new entries and there are allot of prizes available.

tinyIMU v2 inertial measurement unit

tinyIMU V2 is a sensor unit useful for building quadrocopters or other platforms where you need to know the orientation of the given platform. It uses the MMA7455 3-axis accelerometer from Freescale with 10 bit output and the ITG3200 3-axis gyroscope from Invensense with 16 bit output. The PCB was designed to be as small as possible to save weight and space (both important parameters when flying). There is only a 4 pin header present on the PCB for power and I2C lines. The schematics and PCB was designed in Eagle and I’m releasing it under CC BY-NC-SA 3.0 (download link bellow).

This sensor unit has already been used successfully with AeroQuad software and its just a matter of having the right drivers for the sensors to use it with other platforms as well.

here is a video with tinyIMU connected to AeroQuad:
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tinyIMU V2 schematics + PCB

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