Add T-TWR Plus Hardware description page

Add hardware description page with instructions on how to flash tinyuf2
to the radio.

Author: n1zzo

_media/tinyuf2_ttwrplus.jpg

@@ -23,3 +23,4 @@ This table provides a glance on the underlying hardware of each of the supported
 * [Yaesu FT2D](hardware/ft2d.md)
 * [Ailunce HD1](hardware/hd1.md)
 * [Anytone UV878](hardware/uv878.md)
+* [LILYGO T-TWR Plus](hardware/ttwrplus.md)

hardware/hardware.md

@@ -0,0 +1,65 @@
+# LILYGO T-TWR Plus
+
+![T-TWR Plus](../_media/ttwrplus.jpg)
+
+The T-TWR Plus v2.0 is a digital radio, designed and produced by LILYGO, following suggestions from the OpenRTX team.
+This device is based on an ESP32S3 microcontroller, paired with an SA868S baseband. To enable M17 and other digital
+protocols, the SA868S module has to be flashed with [sa8x8-fw](https://github.com/OpenRTX/sa8x8-fw), a Free Software firmware that gives
+OpenRTX full control over the underlying AT1846s radio-on-a-chip.
+
+## Hardware Revisions
+
+### Version 2.0
+
+This version is compatible with OpenRTX, however does not feature connections between the speaker and the MCU, as well as between
+the microphone and the MCU, therefore it cannot operate digital voice protocols such as M17 voice without an external peripheral.
+
+Furthermore this version requires an external programmer to flash the SA868S baseband, the programmer can be built from a [cheap UART dongle](https://a.aliexpress.com/_EwDJlmT), two [1N5817 Schottky diodes](https://a.aliexpress.com/_EIiUAzH), and an [SH1.0 Header](https://www.amazon.it/dp/B01N6S8S21?ref_=cm_sw_r_apin_dp_0KZW8ZN1A1DGZ78AFKYZ). Instructions to build the programmer can be found on [sa8x8-fw GitHub repo](https://github.com/OpenRTX/sa8x8-fw).
+
+### Version 2.1
+
+This version is not released yet and should come with a few improvements:
+
+- The baseband can be programmed from ESP32, not requiring users to build their own programming dongle
+- Paths from ESP32 to speaker and mic have been implemented, allowing an unmodified device to operate M17 Voice communications
+ 
+## Device models
+
+- VHF (134-174MHz)
+- UHF (400-480MHz)
+- VHF OpenEdition (134-174MHz)
+- UHF OpenEdition (400-480MHz)
+
+OpenEdition devices come with an unprogrammed SA868S, even though you can also reprogram non-OpenEdition modules, these SKU can show the manufacturer the size of the community interest towards this device.
+
+## Specifications
+
+* MCU: ESP32-S3-WROOM-1-N16R8
+* Baseband: SA868S
+* Display: 128x64 B/W OLED (SH1106)
+* GPS: L76K GNSS
+* RGB LED: WS2812C
+
+## Flashing
+
+OpenRTX distributes releases for the T-TWR target in [UF2 format](https://github.com/microsoft/uf2).
+If your device does not come with a uf2 compatible bootloader, put your radio into espressif bootloader mode (powering up while holding BOOT key),
+connect it to your pc, and install [tinyuf2](https://github.com/adafruit/tinyuf2) with the following commands:
+
+```
+mkdir tinyuf2; cd tinyuf2
+wget https://github.com/adafruit/tinyuf2/releases/download/0.16.0/tinyuf2-lilygo_ttgo_t_twr_plus-0.16.0.zip
+unzip tinyuf2-lilygo_ttgo_t_twr_plus-0.16.0.zip
+esptool.py --chip auto write_flash 0x0 combined.bin
+```
+
+If you power cycle your radio you should see a screen similar to this:
+
+![T-TWR Plus tinyuf2 screen](../_media/tinyuf2_ttwrplus.jpg)
+
+If you connect your radio to a computer (Linux, Windows or macOS), you should see it appear as a USB block device. Drag the `openrtx_ttwrplus.uf2` file onto the device to flash the radio. Power off the radio by holding PWR (Volume +) button for 10 seconds and press the PWR button again to boot OpenRTX.
+Once the radio has been flashed at least once you can access again the tinyuf2 bootloader by pressing the BOOT (Volume -) button **right after** powering up the radio.
+
+## References
+
+- [T-TWR Plus Schematics](https://github.com/Xinyuan-LilyGO/T-TWR/blob/master/schematic/T-TWR-Plus_Rev2.0.pdf)