fpanels

= fpanels - Go library for Logitech/Saitek flight panels
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--

NOTE: This is work in progress. The code is useable, but not much tested. The API may
still change. The library has been verified to work on Linux and Windows. On macOS 11.1 
I get a "bad access" error code.

This library provides code for interfacing with the following Logitech/Saitek
devices:

- Flight switch panel
- Flight multi panel
- Flight radio panel

Multiple devices of the same type is not supported. For example, you will not
be able to interact with two radio panels.

== The panels

=== Flight switch panel

The flight switch panel has:

- A five position switch
- Thirteen two position switches
- A two position landing gear lever
- Three red/green landing gear indicator LEDs 

The USB vendor:product ID for the panel is 06a3:0d67.

==== Landing gear LEDs

The landing gear LEDs can be enabled by sending a one byte USB control message to the device as follows:

----
00000001 Green N
00000010 Green L
00000100 Green R
00001000 Red N
00010000 Red L
00100000 Red R
xx000000 Not used
----

Enabling both the red and green LED gives a yellow color.

==== Switches

The state of the switches can be obtained by a three byte USB bulk read on
endpoint 1. The bits the bytes are as follows:

----
Byte 1
00000001 BAT
00000010 ALT
00000100 AVIONICS
00001000 FUEL
00010000 DE-ICE
00100000 PITOT
01000000 COWL
10000000 PANEL

Byte 2
00000001 BEACON
00000010 NAV
00000100 STROBE
00001000 TAXI
00010000 LANDING
00100000 OFF
01000000 R
10000000 L

Byte 3
00000001 BOTH
00000010 START
00000100 GEAR UP 
00001000 GEAR DOWN
xxxx0000 Not used
----

=== Flight multi panel

The flight multi panel has:

- A five position switch
- Eight push buttons with individually controlable backlight
- A rotary encoder
- A two position switch
- A two position momentary switch
- A pitch trim rotary encoder
- A two row segment display with five numbers on each row

The text on the left on the segment display is not controllable. The text 
shows the function of the selection switch. When IAS, HDG or CRS is
selected, then only three numbers can be shown on the top row and the
bottom row is blank.

When VS or ALT is selected, then both rows can show 5 numbers each. The 
bottom row can additionally show dashes.

The USB vendor:product ID for the panel 06a3:0d06.

==== Segment display and button LEDs

The segment display and button LEDs are controlled by sending an 11 byte USB
control message to the device. The first five bytes are for the top row, the
second five for the bottom row and the 11th byte controls the button LEDs.
The Logitech software sends 12 bytes, but no function has been found for the 12th
byte. The 12th byte is always sent as 0xff.

The 10 numbers on the segment display are encoded as follows:

----
0000xxxx Binary encoded decimal (0x00 shows 0, 0x01 shows 1, etc.)
00001111 Turns the number off
11011110 Shows a dash on the bottom row (0xde)
----

If 0x0f is set for all 10 numbers then the display is turned off, including the
text on the left of the numbers.

Other values outside the range 0-9 will also turn off the number. The Logitech
software uses 0x0f.

The 11th byte for the push button LEDs are encoded as follows:

----
00000001 AP
00000010 HDG
00000100 NAV
00001000 IAS
00010000 ALT
00100000 VS
01000000 APR
10000000 REV
----

==== Switches, buttons and encoders

The state of the switches can be obtained by a three byte USB bulk read on
endpont 1. The bits the bytes are as follows:

----
Byte 1
00000001 ALT
00000010 VS
00000100 IAS
00001000 HDG
00010000 CRS
00100000 Encoder cw
01000000 Encoder ccw
10000000 AP

Byte 2
00000001 HDG
00000010 NAV
00000100 IAS
00001000 ALT
00010000 VS
00100000 APR
01000000 REV
10000000 Throttle ARM

Byte 3
00000001 Flaps up
00000010 Flaps down
00000100 Pitch down
00001000 Pitch up
xxxx0000 Not used
----

=== Flight radio panel

The flight radio panel has:

- Two seven position function switches
- Two dual rotary encoders
- Two momentary push buttons
- Four five number segment displays

The segment displays can show numbers or dash in each position. In addition
a dot can be displayed in combination with a number.

The vendor:prduct ID for the panel is 06a3:0d05.

==== Segment displays

The segment displays are controlled by sending a 22 byte USB
control message to the device, 5 bytes per display, in the following order:
top left, top right, bottom left, bottom right.

The 20 display numbers are encoded as follows:

----
0000xxxx Binary encoded decimal (0x00 shows 0, 0x01 shows 1, etc.)
00001111 Turns the number off
1101xxxx Adds a dot to the number
1110xxxx Shows dash/minus
----

Two additional bytes have to be sent for it to work on Windows, i.e, 22 bytes
in total. These remaining two bytes can be sent as zero.

==== Switches, buttons and encoders

The state of the switches can be obtained by a three byte USB bulk read on
endpoint 1. The bits in the bytes are as follows:

----
Byte 1
00000001 1 COM1
00000010 1 COM2
00000100 1 NAV1
00001000 1 NAV2
00010000 1 ADF
00100000 1 DME
01000000 1 XPDR
10000000 2 COM1

Byte 2
00000001 2 COM2
00000010 2 NAV1
00000100 2 NAV2
00001000 2 ADF
00010000 2 DME
00100000 2 XPDR
01000000 1 ACT/STDBY
10000000 2 ACT/STDBY

Byte 3
00000001 1 inner encoder cw
00000010 1 inner encoder ccw
00000100 1 outer encoder cw
00001000 1 outer encoder ccw
00010000 2 inner encoder cw 
00100000 2 inner encoder ccw
01000000 2 outer encoder cw 
10000000 2 outer encoder ccw
----