# USB Host Controller (UHC) Firmware Update Guide (Draft)

# Background

The VT132 USB-HID keyboard adapter, the small, red, PCB supplied when you order the USB-HID keyboard option, uses a CH559T microcontroller as a USB Host Controller (UHC).

The UHC runs its own firmware that translates between USB-HID protocols and a high-speed serial protocol for the ESP32 to work with a USB keyboard.

From time-to-time, firmware updates may be released to improve performance, fix bugs or extend the functionality of the UHC.

These firmware updates will be embedded in a release of the VT132 firmware and initiated from within the VT132 Setup screens.

# Update Procedure Overview

The procedure for updating the UHC firmware is:

Update the VT132 to the latest release, following the OTA Firmware Update Guide
Navigate to the SET-UP D screen of the VT132
Press 9 on the keyboard to show the keyboard device status
Press U (uppercase 'U') to start the update process
Follow the on-screen prompts for restarting the VT132 to proceed with the update process

TIP

If you have PS/2 keyboard connector you can still view the keyboard device status on the SET-UP D screen but pressing 'U' will do nothing.

WARNING

While it is safe to perform the UHC firmware upgrade repeatedly, the CH559T microcontroller can only be re-flashed a limited number of times (appoximately 100) before it will fail to re-flash again and may not operate correctly after this time.

It is recommended to only update the UHC firmware when required, as indicated in the release notes for a VT132 firmware update.

# Update Procedure Step-by-Step guide

# Update the VT132 to the latest release

This is documented in the OTA Firmware Update Guide

# Navigate to the SET-UP D screen of the VT132

Press the SETUP key ie. <Alt><SysReq> or <Alt><PrintScreen> to enter the VT132 SET-UP screens
Press 5 three (3) times to navigate to the SET-UP D screen

# Show the keyboard device status

Press 9 on the keyboard to show the keyboard device status
Details of the current UHC firmware version and any attached keyboard will be shown like in this example:

Keyboard device status

# Start the UHC firmware update process

Press U (uppercase 'U') on the keyboard to start the UHC firmware update process
Details of the first UHC firmware update screen are shown here:

UHC firmware upgrade

TIP

As the first two (2) lines of text on this screen suggest, you can abort the update process by pressing reset during the first 5 seconds.

This is only the first point where you can abort the process, there are 2 other opportunities later in the process.

# Proceeding with the update process

As the text on the UHC firmware upgrade screen indicates, you must power-cycle the VT132 to proceed with the update process.
In addition you must jumper/short two (2) pads on the back of the VT132 to force the UHC to restart in programming mode
Diagrams showing the pads to short for both the VT132 for RC2014 and the VT132 Stand Alone editions are given here:
- In the first image the pads are circled in GREEN.
- In the second image you can see how I normally do this with a pair of tweezers.

# VT132 Designed for RC2104 edition

# VT132 Stand Alone edition

# Finishing the update process

# Failure

If you have not successfully forced the UHC to restart in programming mode, you will see the following screen after the restart:
This will also happen if you only reset the VT132 and have not performed a full power cycle
If you see this screen, simply reset the VT132 and start the procedure again

UHC firmware upgrade failure

# Success

If you have successfully forced the UHC to restart in programming mode, you will see the following screen after the restart:
The UHC firmware update will now complete
When you see the GREEN text UHC upgrade complete. the process is finsihed
You must again perform a full power cycle to correctly restart the UHC following the firmware upgrade

UHC firmware upgrade success