I buy parts from Digikey for this reason. They always work. Think how
much money and time you would have saved by spending more on legitimate
components.
On 12/17/2016 1:26 PM, Luka C wrote:
I'm writing this to warn others or ask if anyone had similar
experiences. I purchased a lot of Atmel ATMEGA328P microcontrollers from
a seller on Aliexpress. The lot was listed as "new" in the description
and had a picture of the microcontroller in the reel so I thought it's a
legit new sealed lot. After the package arrived, I noticed the
microcontrollers were not in a real and were just randomly taped on a
piece of some material with some semitransparent tape. I sent the boards
to the local PCB soldering company and they have soldered
microcontrollers on the boards. I flashed the program and the first
board and it worked just fine so I thought I made a great deal because
the price was really good for the lot.
But this is where things became strange, after I was done programming
the first board, I tested the other boards. The results were strange to
say at least. Some of the microcontrollers came in a "state" where any
fuse reprogramming was impossible (btw, SPIEN was not disabled in the
fuses!). Two particular microncontroller samples were really strange.
One seemed to execute really strange sequences of commands without any
reason and my nixie clock would get frozen every now and then. Since I
own the debugger (Atmel ICE), I decided to debug the firmware on the
chip. It turns out that the chip would go really crazy when, for
example, 0 and 5 were displayed on the two middle tubes on my clock. The
debugger call stack showed that one function was executed when it should
not have been and the values of variables in the programmed had values
that in no way could be there in the normal program operation.
Second one had trouble outputting data to the LED controller. Debugging
this one's firmware showed that the microcontroller was not frozen and
in fact was sending data to the LED controller but I guess the data was
not properly formatted or something.
There were some boards with perfectly fine chips so I decided to do a
simple tested. Since my clock consists of 2 boards, one for the
microcontrollers and power supply circuitry and the other one for the
nixie tubes and the LEDs, I decided to do a test and swapped the board
with the tubes and LEDs across both "working" and "faulty"
microcontroller boards. The working ones never produced not a single
fault or glitch, I tried to replicate the bugs on them with no success.
On the other hand, the faulty ones were impossible to fix even by
reflashing the microcontrollers multiple times with the exact same hex
filed used to flash the working ones.
At the end, I am confused. I am not sure what to conclude from this
really. I believe the fault is not in the board itself (PCB layout or
connections) but that it comes from the faulty microcontrollers I have
purchased. After doing a little research on the internet, I found some
people saying that these Chinese companies basically buy used equipment
and remove the microcontrollers from them or that they simply purchased
large quantities of chips that have failed quality control and sells
them at lower prices. I will try to find a way to remove the faulty ones
from the boards and replace them with new ones purchased from RS
Components and then do the tests again.
Anyone ever had similar experiences or has any idea why would this happen?
--
David Forbes, Tucson AZ
--
You received this message because you are subscribed to the Google Groups
"neonixie-l" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to neonixie-l+unsubscr...@googlegroups.com.
To post to this group, send an email to neonixie-l@googlegroups.com.
To view this discussion on the web, visit
https://groups.google.com/d/msgid/neonixie-l/2bf452e0-6da0-fd57-035a-1a9b8cf971b6%40dakotacom.net.
For more options, visit https://groups.google.com/d/optout.
