This document outlines the protocol used during production for testing and the initial provisioning of Trezor devices.
## Commands and Responses
In the production environment, the test equipment sends single-line text commands.
These commands start with the command name and can optionally be followed by parameters separated by spaces.
Command Format:
`COMMAND [INARG1 [INARG2 [INARG3 ...]]]`
Example:
```
CPUID READ
```
The Trezor device responds with single-line text responses that start with either `OK` or `ERROR`, followed by output values separated by spaces.
If the device receives an unrecognized command, it responds with the text `UNKNOWN`.
Device responds with single line text response starting with words `OK` or `ERROR` optionally followed by output values delimited by spaces.
In case of unrecognized command, device responds with text `UNKNOWN`.
Response Format:
`OK [OUTARG1 [OUTARG2 [OUTARG3 ...]]]`
Example:
```
OK 2F0079001951354861125762
```
## List of commands
### PING
The `PING` command serves as a no-operation request, and the device responds with `OK` to acknowledge receipt.
Example:
```
PING
OK
```
### CPUID READ
The `CPUID READ` command reads a 96-bit long unique ID stored in the device's CPU.
The command always returns `OK` followed by a 24-digit hexadecimal value representing the unique ID.
Example:
```
CPUID READ
OK 2F0079001951354861125762
```
### BORDER
The `BORDER` command draws a single white border around the screen on a black background. This command has no input parameters and always returns `OK`.
Example:
```
BORDER
OK
```
### DISP
The `DISP` command draws vertical color bars on the screen based on a list of specified colors provided as a parameter.
Each character in the parameter represents one vertical bar and its color (R - red, B - blue, W - white, any other character - black).
The number of characters corresponds to the number of bars.
Note: On monochromatic displays R, G, B characters are interpreted as the white color.
Example (to draw 6 vertical bars - red, black, green, black, blue and black):
```
DISP RxGxB
```
### BUTTON
The `BUTTON` command tests the functionality of the device's buttons.
It waits for the user to press and release a specified button in a designated timeout period.
The command required two input parameters:
* The first parameter specifies the expected button or combination of buttons, with possible values: LEFT, RIGHT, BOTH.
* The seconds parameter specifies the timeout duration in seconds in range 1 to 9
If the specified button or button combination is not detected within the timeout, the command will return and `ERROR TIMEOUT`.
Example (to wait for 9 seconds for the left button):
```
BUTTON LEFT 9
OK
```
### TOUCH
The `TOUCH` command test the functionality of the display's touch screen.
It draws a filled rectangle in one of the four display quadrants and waits for user interaction.
The command requires two input parameters:
* The first parameter, which should be a value between 0 and 3, determines the quadrant where the rectangle will be drawn.
* The second parameter, a value between 1 and 9, represents the timeout in seconds.
If the display is not touched within the specified timeout, the command will return an `ERROR TIMEOUT`.
Example (to draw a rectangle in the top-left quadrant and wait for 9 seconds for touch input):
```
TOUCH 0 9
OK 50 90
```
### SENS
The `SENS` command is used to evaluating the touch screen sensitivity.
It draws a filled box around the touch coordinates.
It takes one input parameter, a sensitivity, a decimal value representing sensitivity.
Please note that the sensitivity value is model-dependent.
It's important to mention that this command does not return any output.
A device restart is required to stop this operation.
Example:
```
SENS 12
```
### PWM
The `PWM` command sets the display backlight using PWM (Pulse Width Modulation).
This command takes one input parameter, a decimal value between 0 to 255, and adjusts the PWM output to control the display LED backlight.
Example::
```
DISP 128
OK
```
### SD
The `SD` command initiates a simple test of the SD card.
The test includes writing and reading back a few blocks of data and comparing them for equality.
Possible error return codes are:
-`ERROR NOCARD` - Indicates that no SD card is present
-`ERROR sdcard_write_blocks (n)` - Indicates a write failure to the N-th block
-`ERROR sdcard_read_blocks (n)` - Indicates a read failure from the N-th block
-`ERROR DATA MISMATCH` - Indicates a mismatch between the read data and the written data
-`OK` - Indicates that the test has passed successfully
Note: the command returns `UNKNOWN` for models without the SD card support
Example:
```
SD
OK
```
### SBU
The `SBU` command allows you to set the states of SBU1 and SBU2 pins.
It takes two input parameters, each representing the state of one pin (0 or 1), and sets the corresponding output pins accordingly.
Example:
```
// sets SBU1 <-1,SBU2<-0
SBU 1 0
OK
```
### OTP READ
The `OTP READ` command is utilized to retrieve a string parameter from the device's OTP memory.
This string typically contains information identifying the model and production batch of the device.
The command always returns OK followed by the read value.
If the OTP memory has not been written yet, it returns a special response: OK (null).
Example:
```
OTP READ
OK (null)
```
### OTP WRITE
The `OTP WRITE` command enables you to store a string parameter (which can be used to identify the model and production batch, for instance) into the device's OTP memory.
The parameter can be up to 31 characters in length.
Example:
```
OTP WRITE 10002
OK
```
### VARIANT
The `VARIANT` command allows you to write up to 32 decimal values (representing device variant options), each ranging from 0 to 255, and delimited by spaces, into the OTP memory.
Example (to write 8 bytes into OTP memory):
```
VARIANT 128 64 100 1 2 3 0 0
```
### WIPE
This command invalidates the current firmware in the flash memory by erasing its beginning, including metadata.
After performing this operation, it displays the text "WIPED" on the screen and returns the response OK.
Returns the x-coordinate of the FIDO attestation public key stored in Optiga. Can be executed only before the LOCK command is called.
This command can be used to verify that the FIDO attestation key was decrypted and stored correctly by verifying that the returned string of bytes appears in the FIDO attestation certificate.
Example:
```
KEYFIDO READ
OK 0D35A613358EDAB4CA04D05DD716546CD97973DE58516AF6A8F69BEE89BEFAA1
