Program Bootloader of Digispark ATTiny85 with A ISP Programmer Mar 8th 2021 Words: 1.3k

Background

After run micronucleus -run ./upgrade-t85_default.hex on my Chinese clone of Digispark, I successfully break the bootloader so the USB programming interface is no longer available for me.

My kernel log shows the following errors:

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08.03.2021 22:54:17:742	kernel	usb 1-4: new low-speed USB device number 64 using xhci_hcd
08.03.2021 22:54:17:865	kernel	usb 1-4: device descriptor read/64, error -71
08.03.2021 22:54:18:095	kernel	usb 1-4: device descriptor read/64, error -71
08.03.2021 22:54:18:325	kernel	usb 1-4: new low-speed USB device number 65 using xhci_hcd
08.03.2021 22:54:18:449	kernel	usb 1-4: device descriptor read/64, error -71
08.03.2021 22:54:18:679	kernel	usb 1-4: device descriptor read/64, error -71
08.03.2021 22:54:18:789	kernel	usb usb1-port4: attempt power cycle
08.03.2021 22:54:19:442	kernel	usb 1-4: new low-speed USB device number 66 using xhci_hcd
08.03.2021 22:54:19:442	kernel	usb 1-4: Device not responding to setup address.
08.03.2021 22:54:19:649	kernel	usb 1-4: Device not responding to setup address.
08.03.2021 22:54:19:855	kernel	usb 1-4: device not accepting address 66, error -71
08.03.2021 22:54:19:982	kernel	usb 1-4: new low-speed USB device number 67 using xhci_hcd
08.03.2021 22:54:19:982	kernel	usb 1-4: Device not responding to setup address.
08.03.2021 22:54:20:189	kernel	usb 1-4: Device not responding to setup address.
08.03.2021 22:54:20:395	kernel	usb 1-4: device not accepting address 67, error -71
08.03.2021 22:54:20:396	kernel	usb usb1-port4: unable to enumerate USB device
08.03.2021 22:54:50:095	kernel	usb 1-4: new low-speed USB device number 68 using xhci_hcd
08.03.2021 22:54:50:219	kernel	usb 1-4: device descriptor read/64, error -71
08.03.2021 22:54:50:449	kernel	usb 1-4: device descriptor read/64, error -71
08.03.2021 22:54:50:679	kernel	usb 1-4: new low-speed USB device number 69 using xhci_hcd
08.03.2021 22:54:50:802	kernel	usb 1-4: device descriptor read/64, error -71
08.03.2021 22:54:51:035	kernel	usb 1-4: device descriptor read/64, error -71

Solution

Luckily this Digispark I own does not disable the RESET pin(PB5) as the Genuine Digispark does, therefore I still can use the ISP to flash a new bootloader into the ATtiny85.

Tools required

Latest micronucleus command line tool and the ATtiny85 bootloader firmware release from GitHub - Micronucleus

avrdude executable, installed with Ardiono IDE on Linux.

A USB-ISP kit, in this case a USBasp.

Steps

Connetion:

USBasp Digispark
MOSI MOSI (PB0)
MISO MISO (PB1)
SCLK SCLK (PB2)
RESET RESET (PB5)

Run the following command:

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avrdude -cusbasp -pattiny85 -e -v -b19200 -Uflash:w:/<path>/t85_default.hex

To solve the USB permission problem, either use the sudo or create a udev rule.

I did not modify the default fuse setting, but here’s a fuse code calculator for ATtiny85 if of any use.

The default code for my Digispark (PB5 as RESET) is E:FE, H:DF, L:F1

To set the fuse, use the following command:

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avrdude -cusbasp -pattiny85 -e -v -Ulfuse:w:0xf1:m -Uhfuse:w:0xdf:m -Uefuse:w:0xfe:m -Uflash:w:/<path>/t85_default.hex

An example of output(with verbose flag):

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avrdude: Version 6.3, compiled on Jul  7 2020 at 19:38:43
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "/etc/avrdude.conf"
         User configuration file is "/root/.avrduderc"
         User configuration file does not exist or is not a regular file, skipping

         Using Port                    : usb
         Using Programmer              : usbasp
         Overriding Baud Rate          : 19200
         AVR Part                      : ATtiny85
         Chip Erase delay              : 4500 us
         PAGEL                         : P00
         BS2                           : P00
         RESET disposition             : possible i/o
         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     6     4    0 no        512    4      0  4000  4500 0xff 0xff
           flash         65     6    32    0 yes      8192   64    128  4500  4500 0xff 0xff
           signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00
           lock           0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
           lfuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
           hfuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
           efuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
           calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00

         Programmer Type : usbasp
         Description     : USBasp, http://www.fischl.de/usbasp/

avrdude: auto set sck period (because given equals null)
avrdude: warning: cannot set sck period. please check for usbasp firmware update.
avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e930b (probably t85)
avrdude: safemode: hfuse reads as DF
avrdude: safemode: efuse reads as FE
avrdude: erasing chip
avrdude: auto set sck period (because given equals null)
avrdude: warning: cannot set sck period. please check for usbasp firmware update.
avrdude: reading input file "/home/foo/Downloads/t85_default.hex"
avrdude: input file /home/foo/Downloads/t85_default.hex auto detected as Intel Hex
avrdude: writing flash (8166 bytes):

Writing | ################################################## | 100% 0.00s

avrdude: 8166 bytes of flash written
avrdude: verifying flash memory against /home/foo/Downloads/t85_default.hex:
avrdude: load data flash data from input file /home/foo/Downloads/t85_default.hex:
avrdude: input file /home/foo/Downloads/t85_default.hex auto detected as Intel Hex
avrdude: input file /home/foo/Downloads/t85_default.hex contains 8166 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 0.00s

avrdude: verifying ...
avrdude: 8166 bytes of flash verified

avrdude: safemode: hfuse reads as DF
avrdude: safemode: efuse reads as FE
avrdude: safemode: Fuses OK (E:FE, H:DF, L:F1)

avrdude done.  Thank you.

Unplug and plug in the Digispark again, and now the device is recognized correctly. 

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08.03.2021 23:05:02:612	kernel	usb 1-4: new low-speed USB device number 77 using xhci_hcd
08.03.2021 23:05:02:751	vmware-usbarbitrator	USBGL: kevent: adding USB device 1-4
08.03.2021 23:05:02:752	kernel	usb 1-4: New USB device found, idVendor=16d0, idProduct=0753, bcdDevice= 2.05
08.03.2021 23:05:02:753	kernel	usb 1-4: New USB device strings: Mfr=0, Product=0, SerialNumber=0
08.03.2021 23:05:02:770	mtp-probe	checking bus 1, device 77: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-4"
08.03.2021 23:05:03:347	mtp-probe	checking bus 1, device 77: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-4"

Reference

Using and reviving Digispark clones

Configuring the Digispark ATTINY85 board for Arduino IDE and upgrading the bootloader