I bought from various sources a bunch of ATMega328P-U and ATMega328PB-U that I soldered on a custom PCB.
I successfully flashed MiniCore bootloader on each through SPI, and then uploaded a basic sketch to read fuses with an USBtoUART dongle.
Here is what I noted:
- #1 MEGA328P U-TH 35478D 20074PU : bootloader burned successfully ; sketch uploaded successfully at first (tho didn't display Serial.print unless I unplug-replug it) ; sketch upload timed-out on second try ; needed to reburn bootloader to reupload new sketch.
- #2 MEGA328P U-TH 35478D 20074PU : likewise #1
- #3 MEGA328PB -U 2021D TW 2021BH : likewise #1 but never displayed serial prints.
- #4 MEGA328PB -U 20120 TW 2012R82 : likewise #3, never displayed serial prints.
- #5 MEGA328P U-KR 35473D 1950AN6 : everything worked as expected (serial print on first sketch upload, second sketch upload ok as well).
- #6 MEGA328P U-TH 354730 2012SMH : likewise #1
FWIW, chips #4 #6 were bought on Farnell, and the #1 #2 #3 #5 on Aliexpress.
Fuses read on serial prints for all MEGA328P were: Low: 0xE2 ; High: 0xD6 ; Ext: 0xFD ; Lock: 0xCF
Apart from the uC, the PCB is populated with 3 capacitors between each VCC and GND of the uC, various resistors, 2 2N7002 transistors, some buttons and headers.
I can't make any sense out of those logs. Did anyone encountered such behaviour?