Can an ATMega328p be bricked such that it cannot be programmed but still works?

Question

I cannot update the program on my ATMega328p-AU (with the old version of the Arduino nano bootloader burnt to it). Oddly enough I can still talk to the program running on the uC (query and read out some values, switch stuff on and off) via serial. I am using the Arduino IDE for programming and serial communication.

I first tried using two different USB-TTL programmers. The 0.1 uF cap between DTR and Reset is on the board hosting the uC. The error was stk500_getsync() attempt 1 of 10: not in sync: resp=0x00 (whole error below).

Then I used an Arduino Nano (328p, old bootloader) with the ArduinoISP sketch flashed to it. I can neither reprogram the sketch nor reburn the boot loader. The error given is (whole error below):

avrdude: Device signature = 0x000000
avrdude: Yikes!  Invalid device signature.
         Double-check connections and try again, or use -F to override
         this check.

I am afraid of using the -F option as I fear the uC will stop working altogether.

Is my uC bricked and just working by chance? I have checked and rewired the connections many times, and I am confident that they are correct.

Error using USB-TTL programmer:

Sketch uses 12774 bytes (41%) of program storage space. Maximum is 30720 bytes.
Global variables use 611 bytes (29%) of dynamic memory, leaving 1437 bytes for local variables. Maximum is 2048 bytes.
/opt/arduino-1.8.10/hardware/tools/avr/bin/avrdude -C/opt/arduino-1.8.10/hardware/tools/avr/etc/avrdude.conf -v -patmega328p -carduino -P/dev/ttyUSB0 -b57600 -D -Uflash:w:/tmp/arduino_build_408838/nixie.ino.hex:i
avrdude: Version 6.3-20190619
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "/opt/arduino-1.8.10/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/home/user/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/ttyUSB0
         Using Programmer              : arduino
         Overriding Baud Rate          : 57600
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x00
avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0xe0
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0xe0

avrdude done.  Thank you.

An error occurred while uploading the sketch

Error using Arduino Nano as ISP or using it to burn the bootloader:

avrdude: Version 6.3-20190619
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "/opt/arduino-1.8.10/hardware/tools/avr/etc/avrdude.conf"
         User configuration file is "/home/user/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : /dev/ttyUSB0
         Using Programmer              : stk500v1
         Overriding Baud Rate          : 19200
         AVR Part                      : ATmega328P
         Chip Erase delay              : 9000 us
         PAGEL                         : PD7
         BS2                           : PC2
         RESET disposition             : dedicated
         RETRY pulse                   : SCK
         serial program mode           : yes
         parallel program mode         : yes
         Timeout                       : 200
         StabDelay                     : 100
         CmdexeDelay                   : 25
         SyncLoops                     : 32
         ByteDelay                     : 0
         PollIndex                     : 3
         PollValue                     : 0x53
         Memory Detail                 :

                                  Block Poll               Page                       Polled
           Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
           ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
           eeprom        65    20     4    0 no       1024    4      0  3600  3600 0xff 0xff
           flash         65     6   128    0 yes     32768  128    256  4500  4500 0xff 0xff
           lfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           lock           0     0     0    0 no          1    0      0  4500  4500 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00

         Programmer Type : STK500
         Description     : Atmel STK500 Version 1.x firmware
         Hardware Version: 2
         Firmware Version: 1.18
         Topcard         : Unknown
         Vtarget         : 0.0 V
         Varef           : 0.0 V
         Oscillator      : Off
         SCK period      : 0.1 us

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x000000 (retrying)

Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x000000 (retrying)

An error occurred while uploading the sketch
Reading | ################################################## | 100% 0.02s

avrdude: Device signature = 0x000000
avrdude: Yikes!  Invalid device signature.
         Double check connections and try again, or use -F to override
         this check.


avrdude done.  Thank you.

Answer 1

yes, that's what programming fuses are for.

We wouldn't call that "bricked", though.

"Bricked" is a relatively new term that describes a device that was converted from functional device (which yours still is) to something that is only useful as paperweight/building material.

Answer 2

I had something similar happen with an Arduino uno, if your program is outputting on serial you are blocking programming. You need to upload a sketch (ie blink) and reset the Arduino at just the right time when it will start the transfer. A few tries may be necessary to get the timing right. If you succeed, I recommend you place a Delay loop in your future program to give you some programming window time before flooding the serial port with data...