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Apple TV 4K

The Apple TV 4K starts at $179 for 32GB of storage, and $199 for 64GB. Its firmware identifier is AppleTV6,2. It is capable of playing 4K content.

The Apple TV 4K was announced on 12 September 2017 and released on 22 September 2017.

Application processor

The Apple TV 4K makes use of the Apple A10X processor.

Debug Port

AppleTV4K Debug Ethernet.jpg

Hidden behind a small trapdoor in the back of the Ethernet port is a debug port that includes USB access.

Without a custom cable the easiest method of access to the port is to solder directly onto the pins. Care should be taken with the test points that are near the port as they also serve as the top of the via that connects the debug port to the rest of the Apple TV. USB access is enabled by setting the voltage on the mode pin to either USB device mode or assert force_dfu mode. While in DFU or recovery Apple's firmware does not care about the mode pin state and always enables USB. In assert force_dfu mode the Apple TV will enter DFU on every boot.

AppleTV4K Debug Internal.jpg

Pin Name Max Voltage Notes
1 Unknown 1.8V Purpose of the pin is unknown but it is connected to the A10X near the USB pins
2 ACC_PWR 3.3V Pin is connected to a power switch, more exploration is required to see if it is capable of outputting 5V
3 USB_DM 3.3V Pin operates at USB logic levels.
4 USB_DP 3.3V Pin operates at USB logic levels.
5 GND 0V Pin is connected directly to the boards ground plane
6 Mode Pin 1.8V Selects mode dependant on voltage
7 Unknown 1.8V See pin 1, connected to the A10X next to pin 1

Mode Pin

Pin 6 in the debug connector is a mode select pin. There are 4 known modes available.

VMin VMax Function
0V 0.49V Disabled
0.51V 0.76V USB Device mode active
0.76V 0.99V Assert force_dfu
1.01V 1.8V Reset device

USB Device mode is active from 0.5-0.99V After 0.99V the device will enter a reset loop. Force_dfu is asserted with voltages above 0.76V, and will enter DFU on reboot. To trigger a reboot and enter DFU from the port alone without an external reboot requires first raising the voltage about 1.01V then dropping it no lower than 0.76V. The transition between each mode results in metastability for ±10mV from the transition point (0.50V, 0.75V, 1.00V) between modes.