Summary of How to fix dead atmega and attiny avr chips
Atmega Fusebit Doctor is a simple, low-cost device that repairs bricked Atmega and Attiny AVRs by reprogramming factory fusebits using high-voltage parallel/serial programming. It supports many AVR models via three on-board DIP sockets and adapters, can force entry into programming mode even with wrong clock settings, and optionally erases flash/eeprom to clear lockbits. Status LEDs and USART output report progress and results. The tool uses factory fuse settings (internal 8MHz clock, EESAVE enabled) and is based on HV programming procedures from AVR datasheets.
Parts used in the Atmega Fusebit Doctor:
- DIP28 socket (Atmega8 compatible)
- DIP20 socket (Attiny2313 compatible)
- DIP40 socket (Atmega32 compatible)
- Goldpin connector for external adapters
- HVPP adapter (for DIP20-B Attiny26 and DIP40-B Atmega8515)
- HVSP adapter (for DIP8 Attiny13 and DIP14 Attiny24)
- START pushbutton
- ALLOW ERASE jumper
- Status LEDs (green and red)
- USART serial connector
- Wiring/traces to RDY/BSY and parallel programming signals
Atmega fusebit doctor, as name says it, device for repairing dead Atmega and Attiny family AVRs by writing fabric fusebits. Most common mistakes or problems are a wrong clock source (CKSEL fusebits), disabled SPI programming (SPIEN fuse) or disabled reset pin (RSTDISBL fuse). This simple and cheap circuit will fix you uC in a fraction of a second.
If in first case we can help ourself with clock generator, then in 2nd and 3rd cases bring uC back to life is impossible with standard serial programmer. Most of people do not decide to build parallel programmer because its inconvenient and its cheaper and faster to buy new uC.
Step 1: Sockets
This circuit use the high-voltage parallel and serial programming method. Atmega8(doctor) has saved in it’s memory signatures of 96 (so far) AVR Atmega and Attiny uC’s, just put your dead avr in socket, press the START button, and enjoy your good-as-new processor.
There are three slots on board, for most common AVR’s, pins compatible with: DIP28 Atmega8, DIP20 Attiny2313, and DIP40 Atmega32 compatible processors.
There is also an extra goldpin connector with all signals so you can attach adapters:
-the “#1 HVPP adapter” with DIP20-B Attiny26 and DIP40-B Atmega8515 compatible
-the “HVSP adapter” for tiny DIP8 Attiny13 and DIP14 Attiny24 compatible.
-your own adapters for other types of processors, in trough-hole or surface-mounted, you can use the breadboard for this – just connect signals to correct pins. How? Check your AVR datasheet, go to “memory programming” and then “parallel programming” – check the signal names, all signals are described under the DIP40 slot.
Step 2: Montage note
ATTENTION! While mounting the DIP40 slot, you must to remove it pins from 29 to 37. These pins must not have electrical contact with inserted uC pins. Take a look at this pic, these you must remove from slot:
Step 3: Other
Leds explanation:
green on – patient successfully cured, fusebits repaired. If lockbits are enabled, just verify fusebits with factory ones – and if they ok – light up green.
red on – signature problem, can’t read, no device in socket, or no such signature in database.
green flashing – signature ok, fusebits are wrong. Lockbits enabled, chip erase permission required (read below).
red flashing – signature ok, no lockbits, but for some reason can’t write new fusebits.
The ALLOW ERASE jumper allows doctor to erase whole flash and eeprom memory, if it is open, doctor will newer erase memory but may not cure device if lockbits are enabled, so you choose. After insert dead uC and press the START button, doctor will initiate the parallel programming mode. If our patient will not respond with high state at RDY/BSY line, doctor will use other way to initiate programming mode even if the XTAL pins are switched to external resonator. After that doctor will erase whole memory if user allows that. Then, read device signature and check if it supports it. Next are lockbits checked, and if they not blocking device, doctor sets all fusebits to fabric, having regard to whether there are extended fusebits or not. After that fusebits are verified, and proper leds are flashed. Also, all the info are send trough usart.
Code was written based on high-voltage parallel programming section of datasheet of suitable AVRs.
Fusebits: Internal 8MHz clock, and enabled EESAVE bit.
For more detail: How to fix dead atmega and attiny avr chips
- What does Atmega Fusebit Doctor fix?
It repairs dead Atmega and Attiny AVRs by writing factory fusebits using high-voltage programming. - How many AVR signatures does the device store?
It has saved signatures of 96 AVR Atmega and Attiny microcontrollers so far. - Can it recover chips with wrong clock source?
Yes, it can enter programming mode even if XTAL pins are set to an external resonator and can handle wrong clock source. - Can it recover chips with SPIEN or RSTDISBL disabled using a standard serial programmer?
No, if SPIEN or RSTDISBL are disabled, standard serial programmers cannot recover the chip; this device uses high-voltage methods to restore them. - What sockets are available on the board?
There are three sockets: DIP28 for Atmega8, DIP20 for Attiny2313, and DIP40 for Atmega32-compatible processors. - Do I need to modify the DIP40 socket during assembly?
Yes, pins 29 to 37 must be removed from the DIP40 socket so they do not contact the inserted MCU pins. - What do the LEDs indicate?
Green on means fusebits repaired; red on means signature or device read problem; green flashing means signature OK but lockbits block writing; red flashing means signature OK but writing fusebits failed. - What does the ALLOW ERASE jumper do?
If closed, the doctor will erase flash and eeprom memory to clear lockbits; if open, it will never erase memory which may prevent curing devices with lockbits enabled. - Are adapters supported for other packages?
Yes, a goldpin connector provides signals for attaching HVPP, HVSP, or custom adapters, and a breadboard can be used for custom connections following the AVR datasheet signals. - What fusebits are written by default?
The device writes factory fusebits including internal 8MHz clock and enabled EESAVE bit.
