Improved xh-hk4401 docs (#550)

- Changed order so FTDI is first since this is the easier option
- Changed the circuit for the inverter to one that is easier to
  make and is safer (doesn't send 5v to RPi GPIO and prevents
  back power)
- Added table to show which uart to use based on which method
  is used
- Added connetion details to FTDI method
- Added note about checking if FTDI settings are saved
pull/555/head
Sebastian Goscik 3 years ago committed by GitHub
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@ -30,40 +30,50 @@ connected to the main KVM via a micro USB cable, however this is **NOT** as USB
The control unit communicates to the KVM using the RS-232 protocol (at 5v) not USB, and one of the following The control unit communicates to the KVM using the RS-232 protocol (at 5v) not USB, and one of the following
solutions must be used. solutions must be used.
### Inverting USB UART adapter (FT-232) - The easy way
### An inverter circuit Some USB UART adapters have the rare feature to invert the logic level of the RX/TX signals. For example the FTDI FT232 can
be configured via the FTDI configuration GUI to do this. With such an adapter, the circuit above is not required. All you
need is to connect it to a micro-USB connector.
For this you will need: !!! warning
These options will only work on UART adapters with **genuine** FTDI chips. There are a lot of cheap fakes on the
market that either lack this option, or will prevent you from changing the settings. To avoid getting a fake
ensure you always purchase from a reputable store and brand (Adafruit, Sparkfun, etc.), Amazon **is not** a
reputable store.
* 2x 2n7000 MOSFETs In order to invert the RX/TX signals, you can use [ft_prog](https://ftdichip.com/utilities/#ft_prog) and set the
* 2x 10K resistors following settings:
* 1x USB Micro connector, or sacrificial micro USB cable
* *Optional:* USB UART adapter
<img src="xh-hk4401_circuit.jpg" /> <img src="ft232_config.png" />
You can connect this either via a USB UART adapter, or directly to the Raspberry Pi: `GND -> Pin 6`, `TX -> Pin 8`, `RX -> Pin 10`. Once the UART is configured, please fully disconnect it and connect it back to the computer. Relaunch `ft_prog` and ensure the settings are still set. If they are not, you have a *fake* FTDI chip.
On the v3 PiKVM hat you will need to disable the UART jumpers to use the on-board UART.
!!! note Finally, you will need to connect it to the micro USB port (**This it not a normal USB micro port.**)
Please search online for USB pinouts to ensure you connect it properly. like so:
| Signal | Colour | FT232 Pin |
| ------ | ------ | --------------------------------------------------- |
| Vbus | Red | 5v (if you want to power the KVM from the Pi's USB) |
| D- | White | RX |
| D+ | Green | TX |
| Gnd | Black | GND |
### Inverting USB UART adapter
Some USB UART adapters have the rare feature to invert the logic level of the RX/TX signals. For example the FTDI FT232 can ### An inverter circuit - The cheap way
be configured via the FTDI configuration GUI to do this. With such an adapter, the circuit above is not required. All you
need is to connect it to a micro-USB connector.
In order to invert the RX/TX signals, you can use [ft_prog](https://ftdichip.com/utilities/#ft_prog) and set the following settings: For this you will need:
<img src="ft232_config.png" /> * 1x 74HC14
* 1x USB A socket, or sacrificial micro USB cable
* Optional 1x Diode - If you want to power the KVM from the Raspberry Pi
* 1x 5-pin header
* 5x Female - Female jumper cables
!!! warning <img src="xh-hk4401_circuit.png" />
These options will only be available on UART adapters with genuine FTDI chips. There are a lot of cheap fakes on the
market that either lack this option, or will prevent you from changing their settings. To avoid getting a fake !!! note
ensure you always purchase from a reputable store and brand (Adafruit, Sparkfun, etc.), Amazon **is not** a Please search online for USB pinouts to ensure you connect it properly.
reputable store.
## Adding UI elements to control the KVM switch ## Adding UI elements to control the KVM switch
@ -73,7 +83,12 @@ The UI can be updated to add buttons to switch between KVM inputs and indicators
2. Enable read-write mode on the sd card via `rw` 2. Enable read-write mode on the sd card via `rw`
3. Edit the `/etc/kvmd/override.yaml` file and include the following. Note the assumption that you are using a USB UART present on `/dev/ttyUSB0`: 3. Edit the `/etc/kvmd/override.yaml` file and include the following.
| Method | Device |
|----------|----------------|
| FT-232 | `/dev/ttyUSB0` |
| Inverter | `/dev/ttyAMA0` |
```yaml ```yaml
kvmd: kvmd:

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