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? -- 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/c3f5f01f-0494-4912-a8f6-3d5b4be2d564%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
