i know this topic has been covered tons of times on this forum but i'm still not able to find a solution, so here i am :)
As the title says, my problem is that i'm not able to enter program mode trying to program a brand new ATMEGA32u4 on my custom board through the ISP port. At first, let me give you some details:
Software: Atmel Studio 7.0
Notes on the MCU circuit:
- MCU soldered "as is";
- HWB pulled to Vcc;
- Murata resonator 8MHz (capacitors built-in);
- Circuit is based on the schematic of Feather Lora by Adafruit;
- USB and ISP connector available on my custom board. MISO, MOSI, SCK, RST, VCC, GND are connected to a 50mil-spacing 3x2 connector and mapped following ATMEL-ICE Adapter specifics; USB is connected through 22Ohm resistors as required;
- MCU is supplied by a 3.3V regulator (there are capacitors on VCC terminals even if not visible in the following schematic);
This is the schematic i'm using:
When i connect my board to PC using USB the device shows up in device manager:
When i use USB i'm able to see the device in Device Programming as "ATmel Mega DFU" and read correctly Device signature ("0x1E9587") but i'm not able to "Read..." memories (Flash/EEPROM). I didn't try to erase or program because i'm afraid to worse the situation.
If i use ISP with Atmel ICE I'm able to read Vcc target and nothing else because of "Cannot enter programming mode..." error.
I checked wiring for ISP and probed the resonator and verified there is a 8MHz at XTAL inputs of MCU.
I think there is a fuses setting problem, but i'm not able to understand if and what i can do to solve. The objective is being able to set fuses (and, lately, to burn a bootloader inside).
Any help is appreciated.