user23610: I have a digispark that I want to reprogram, soldered into a circuit. I have burned the default t85 micronucleus firmware. 
This is the command I used:
"C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avrdude" -C "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf" -v -pattiny85 -cstk500v1 -PCOM4 -b19200 -Uflash:w:D:\Documents\micronucleus-master\firmware\releases\t85_default.hex:i

avrdude: Version 6.3, compiled on Sep 12 2016 at 17:24:16
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"

         Using Port                    : COM4
         Using Programmer              : stk500v1
         Overriding Baud Rate          : 19200
         AVR Part                      : ATtiny85
         Chip Erase delay              : 400000 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    12     4    0 no        512    4      0  4000  4500 0xff 0xff
           flash         65     6    32    0 yes      8192   64    128 30000 30000 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 : 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% 0.03s

avrdude: Device signature = 0x1e930b (probably t85)
avrdude: safemode: hfuse reads as D7
avrdude: safemode: efuse reads as FF
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "D:\Documents\micronucleus-master\firmware\releases\t85_default.hex"
avrdude: writing flash (8116 bytes):

Writing | ################################################## | 100% 0.07s

avrdude: 8116 bytes of flash written
avrdude: verifying flash memory against D:\Documents\micronucleus-master\firmware\releases\t85_default.hex:
avrdude: load data flash data from input file D:\Documents\micronucleus-master\firmware\releases\t85_default.hex:
avrdude: input file D:\Documents\micronucleus-master\firmware\releases\t85_default.hex contains 8116 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 0.07s

avrdude: verifying ...
avrdude: 8116 bytes of flash verified

avrdude: safemode: hfuse reads as D7
avrdude: safemode: efuse reads as FF
avrdude: safemode: Fuses OK (E:FF, H:D7, L:F1)

avrdude done.  Thank you.

I have not set any fuses (I hope the frequency is right.)
The board is recognized by my computer and I can program a sketch into it using Arduino IDE. Despite all this the program I burned into it does not run. It seems it is stuck into the bootloader section.
The sketch:
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(0, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(0, HIGH); 
}

Pin PB0 has never a voltage bigger than 1.7V(noise or floating). All pins have similar voltages (except PB3,PB4 which are pulled up or high)
The schematic:

The circuit works. I tested both displays previously with the atiny which I directly programmed with the Uno. The upper right connector is directly plugged into the digispark with the following pins: VIN,GND,5V. The middle connector is also plugged into the digispark.
I have tried:

Powered by USB: I am afraid this will be detected by the bootloader and enter the programming state thus never running the schematic(shouldn't happen but you never know...)
Powered by VIN with a 9V battery. Nothing. All voltages are in check (5V pin has 5v on it. All other pins are floating)
Powered by 5V pin using an Arduino UNO as the source. Nothing.
In all cases the voltage on PB0 stays the same. It varies between 0.6V and 1.6V. 

In Arduino IDE:

Tried Digispark 16.5Mhz
Digispark Pro 16Mhz
Digispark(No Usb) 16Mhz

Always a succesfull uploading. 
Notes:

After uploading in Arduino this text comes up: 

Starting the user app ...
  running: 100% complete

So it is supposed to run the program but the board actually resets because it gets renumerated by windows.
It's not quite possible to de-solder it and program the sketch directly with Arduino as ISP 
I use Windows 10
Fuses used when I burned the micronucleus L:F1 H:D7 E:FF. These are the default "safe" values. The actual fuses needed by the firmware are L:E1 H:DD E:FE.
Difference in extended fuse: Self-programming is curently disabled...Is this the culprit?
I managed to desolder PB0,PB1 and PB2 from the back of the pcb. Now I can't program it directly with Arduino as ISP. The setup I have should work because I can easily program an t45. So it has something to do with the digispark. Checked the connection between pins and the actual MCU. The error I get is Yikes... and sometimes it finds an 0x00ff00 or other junk id for the board but probably it's because of misconnection.

Question #2:
In the current configuration(soldered) would it be possible to use again  Arduino as ISP to program it?  PB0,PB1,PB2 are connected to Serial Clock,Serial Data and Serial Storage Clock respectively. I am trying right now to set the right fuses but every time I get this:
avrdude -C "C:\Program Files (x86)\Arduino\hardware\tools\avr\etc\avrdude.conf" -c stk500v1 -p attiny85  -U lfuse:w:0xe1:m -U hfuse:w:0xdd:m -U efuse:w:0xfe:m -B 20 -b19200 -P COM7

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.06s

avrdude: Device signature = 0x000000 (retrying)

Reading | ################################################## | 100% 0.05s

avrdude: Device signature = 0x000000 (retrying)

Reading | ################################################## | 100% 0.05s

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.

make: *** [fuse] Error 1


user23610: Solved it! I don't know what the real issue was but I constructed a HV programmer and just blasted the digispark with the new and proper fuses. Now it works as it should.

23610: <p>I have a digispark that I want to reprogram, soldered into a circuit. I have burned the default t85 micronucleus firmware. </p>

<p><strong>This is the command I used:</strong></p>

<pre><code>"C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avrdude" -C "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf" -v -pattiny85 -cstk500v1 -PCOM4 -b19200 -Uflash:w:D:\Documents\micronucleus-master\firmware\releases\t85_default.hex:i

avrdude: Version 6.3, compiled on Sep 12 2016 at 17:24:16
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2014 Joerg Wunsch

         System wide configuration file is "C:\Program Files (x86)\Arduino\hardware\tools\avr/etc/avrdude.conf"

         Using Port                    : COM4
         Using Programmer              : stk500v1
         Overriding Baud Rate          : 19200
         AVR Part                      : ATtiny85
         Chip Erase delay              : 400000 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    12     4    0 no        512    4      0  4000  4500 0xff 0xff
           flash         65     6    32    0 yes      8192   64    128 30000 30000 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 : 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% 0.03s

avrdude: Device signature = 0x1e930b (probably t85)
avrdude: safemode: hfuse reads as D7
avrdude: safemode: efuse reads as FF
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "D:\Documents\micronucleus-master\firmware\releases\t85_default.hex"
avrdude: writing flash (8116 bytes):

Writing | ################################################## | 100% 0.07s

avrdude: 8116 bytes of flash written
avrdude: verifying flash memory against D:\Documents\micronucleus-master\firmware\releases\t85_default.hex:
avrdude: load data flash data from input file D:\Documents\micronucleus-master\firmware\releases\t85_default.hex:
avrdude: input file D:\Documents\micronucleus-master\firmware\releases\t85_default.hex contains 8116 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 0.07s

avrdude: verifying ...
avrdude: 8116 bytes of flash verified

avrdude: safemode: hfuse reads as D7
avrdude: safemode: efuse reads as FF
avrdude: safemode: Fuses OK (E:FF, H:D7, L:F1)

avrdude done.  Thank you.
</code></pre>

<p>I have not set any fuses (I hope the frequency is right.)</p>

<p>The board is recognized by my computer and I can program a sketch into it using Arduino IDE. Despite all this the program I burned into it does not run. It seems it is stuck into the bootloader section.</p>

<p><strong>The sketch:</strong></p>

<pre><code>void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(0, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(0, HIGH); 
}
</code></pre>

<p>Pin <code>PB0</code> has never a voltage bigger than <code>1.7V</code>(noise or floating). All pins have similar voltages (except <code>PB3</code>,<code>PB4</code> which are pulled up or high)</p>

<p><strong>The schematic:</strong>
<a href="https://i.stack.imgur.com/B1dOC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/B1dOC.png" alt="enter image description here"></a></p>

<p>The circuit works. I tested both displays previously with the atiny which I directly programmed with the <code>Uno</code>. The upper right connector is directly plugged into the <code>digispark</code> with the following pins: <code>VIN</code>,<code>GND</code>,<code>5V</code>. The middle connector is also plugged into the <code>digispark</code>.</p>

<p><strong>I have tried:</strong></p>

<ul>
<li>Powered by USB: I am afraid this will be detected by the bootloader and enter the programming state thus never running the schematic(shouldn't happen but you never know...)</li>
<li>Powered by VIN with a 9V battery. Nothing. All voltages are in check (<code>5V pin</code> has <code>5v</code> on it. All other pins are floating)</li>
<li>Powered by <code>5V pin</code> using an <code>Arduino UNO</code> as the source. Nothing.
In all cases the voltage on PB0 stays the same. It varies between <code>0.6V</code> and <code>1.6V</code>. </li>
</ul>

<p><strong>In Arduino IDE:</strong></p>

<ul>
<li>Tried Digispark 16.5Mhz</li>
<li>Digispark Pro 16Mhz</li>
<li>Digispark(No Usb) 16Mhz</li>
</ul>

<p>Always a succesfull uploading. </p>

<p><strong>Notes:</strong></p>

<ul>
<li><p>After uploading in Arduino this text comes up: </p>

<blockquote>
  <p>Starting the user app ...
  running: 100% complete</p>
</blockquote>

<p>So it is supposed to run the program but the board actually resets because it gets renumerated by windows.</p></li>
<li><p>It's not quite possible to de-solder it and program the sketch directly with <code>Arduino</code> as <code>ISP</code> </p></li>
<li>I use Windows 10</li>
<li>Fuses used when I burned the <code>micronucleus</code> <code>L:F1</code> <code>H:D7</code> <code>E:FF</code>. These are the default "safe" values. The actual fuses needed by the firmware are <code>L:E1</code> <code>H:DD</code> <code>E:FE</code>.</li>
<li>Difference in extended fuse: Self-programming is curently disabled...Is this the culprit?</li>
<li>I managed to desolder <code>PB0</code>,<code>PB1</code> and <code>PB2</code> from the back of the pcb. Now I can't program it directly with <code>Arduino as ISP</code>. The setup I have should work because I can easily program an t45. So it has something to do with the digispark. Checked the connection between pins and the actual MCU. The error I get is <code>Yikes...</code> and sometimes it finds an 0x00ff00 or other junk id for the board but probably it's because of misconnection.</li>
</ul>

<p><strong>Question #2:</strong></p>

<p>In the current configuration(soldered) would it be possible to use again  <code>Arduino as ISP</code> to program it?  <code>PB0</code>,<code>PB1</code>,<code>PB2</code> are connected to <code>Serial Clock</code>,<code>Serial Data</code> and <code>Serial Storage Clock</code> respectively. I am trying right now to set the right fuses but every time I get this:</p>

<pre><code>avrdude -C "C:\Program Files (x86)\Arduino\hardware\tools\avr\etc\avrdude.conf" -c stk500v1 -p attiny85  -U lfuse:w:0xe1:m -U hfuse:w:0xdd:m -U efuse:w:0xfe:m -B 20 -b19200 -P COM7

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.06s

avrdude: Device signature = 0x000000 (retrying)

Reading | ################################################## | 100% 0.05s

avrdude: Device signature = 0x000000 (retrying)

Reading | ################################################## | 100% 0.05s

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.

make: *** [fuse] Error 1
</code></pre>
 23610: <p>Solved it! I don't know what the real issue was but I constructed a HV programmer and just blasted the digispark with the new and proper fuses. Now it works as it should.</p>
