I was struggling with feedback from devices when performing jailbreak so here's possible behaviour of them so it is clearer if everything going wrong or not.
(ATV 3,1 A1427, Mac)
Micro-USB cable should be capable putting ATV to recovery mode when connected to computer. AFAIK it needs only VCC, D-, D+, GND lines connected. ATV should show up in System Information - USB. On TV it should show picture with white wire. All operations can be performed with TV connected. WiFi connection on ATV is enough. Maybe if DNS settings altered on ATV, they should be changed to automatic.
Checkm8 can be performed with Arduino Uno and Arduino Mega with Keyes USB Host Shield (Blue) or "Arduino Meets Android " USB Host Shield (White). Software: Arduino IDE and it installs Arduino drivers. It was reported that you need genuine Arduino (with FTDI chip) but thats because maybe guys didn't have CH340 chip drivers for Arduino clones. It doesn't go with Arduino IDE but can be easily found (search CH340 driver).
Prepare strictly how Checkm8 author describes it and upload .ino sketch to Arduino.
Connect micro-USB to USB host shield on Arduino, and Arduino connect to computer with USB. Open Arduino terminal, select speed 115200 baud. It will display message "Non Apple DFU found (vendorId: 1452, productId: 4737)"
Checkm8 need ATV in DFU mode. Enter DFU by pushing MENU+DOWN on remote.
When ok it will show
heap feng-shui
Stall status: 5
heap_feng_shui_req: setup status = 0, data status = 4
heap_feng_shui_req: setup status = D, data status = 4
...
set global state
OUT pre-packet: 0
Send random 0x40 bytes: 0
Send random 0x40 bytes HS: 0
Send zero length packet: 0
Send get status #1: 0
Send get status #2: 0
data: 0
data: 0
...
heap occupation
heap_feng_shui_req: setup status = 0, data status = 0
overwrite sending ...
SETUP: 0
OUT (pre packet): 0
OUT: 0
payload sending ...
SETUP: 0
OUT (pre packet): 0
...
Done!
Now connect Micro-USB to computer. May need to power-cycle ATV because Blackb0x needs it in Recovery, not DFU.
Open Blackb0x.app It should show window with your ATV picture and model. Push that picture, choose Install Jailbreak, follow instructions on how to put it in DFU. Good situation is when it shows multiple progress bars like "Downloading iBSS", etc. It will successfully finish somewhere after "Uploading Ramdisk" and it will invite to reboot ATV and connect to TV.
Disconnect Micro-USB and connect ATV to TV and power-cycle it.
When ATV boots, it will show normal ATV interface with no changes. After 5-10 minutes screen goes black and ATV reboots. When it show interface again, you'll see NitoTV and Kodi icons next to Settings on the main screen.
I was struggling with feedback from devices when performing jailbreak so here's possible behaviour of them so it is clearer if everything going wrong or not.
(ATV 3,1 A1427, Mac)