I have bough one Pro Mini, allegedly 5V, 16MHz. Looking at the back side, they are barely visible marks 8M, 16M, 3.3 and 5, but nothing is checked. Made in China of course, it was 4 Euro, though in electronic shop.
On front side, most of the surface of the plastic packages are melted, including on voltage regulator. Only metal(ish) part is tiny, probably 3 stands/legs crystal with barely seen mark AX or something like that, seen under 5x magnified glass.
Without detail testing, I hope that is what I order (5V, 16MHz) and I will perform that during weekend.
What are the packages and marks on such small SMD resonator/crystal for 8/16/20MHz usually can be found on Pro Mini, Made in China? Same for voltage regulators.
spycatcher2k:
You could use an oscilloscope to measure the frequency of the crystal.
I do not have any and as well buying from the shop is necessary to check any item, as it is quite unpredictable what you will get. Once I ordered 50x BF256A, ended actually with 50xBC547. With SMD is quite easier to end with unwanted stock. Additional complaints are not accepted. Similar with different modules, especially comes from China without proper identification.
Ironically, other source than stock from China are quite difficult to fine or it is 2x-10x more expensive (!), while stock from China are 2x more expensive. Have no much choice really, my hands are tied except to double check what I'm actually receiving, while it is possible.
noob314:
What are the packages and marks on such small SMD resonator/crystal for 8/16/20MHz usually can be found on Pro Mini, Made in China? Same for voltage regulators.
Sometimes the resonators on 8Mhz Pro Minis have an 8 on them, but not always.
The markings on the back just need to be ignored, they might be right only.
As for markings on voltage regulators, thats guesswork.
PaulRB:
Connect 7~9V power to the RAW pin and measure the voltage on VCC pin. If its 5V, it will almost certainly be 16MHz. If its 3.3V it will be 8MHz.
This. 20MHz boards are basically unknown in the wild
(probably because the official core doesn't support it; and even if you add the board definition to the official core, a few things are at least slightly broken; off the top of my head, micros() is off by 1/16th (the implementation in the official AVR core only works correctly if 64 divides evenly by the speed in MHz, because it divides 64 (the millis timer prescaler) by the number of clock cycles per microsecond, and the result is truncated because it's done with integers - floats are too slow, too, so you can't use floats either!) - I think MiniCore does 20MHz correctly; I dealt with it using a combination of integer addition/subtraction and bitshift operations for each speed ATTinyCore supports)