Update firmware build instructions

README.md

@@ -5,7 +5,7 @@ Long range, low power messaging system based on Meshtastic relays suitable for u
 # Design principles
 Natural caves are challenging as it comes to communications due to irregular cavity shapes, presence of water and general difficulty of installing any kind of equipment in an environment where everything has to be carried on human's back over hundreds of meters vertically. There are numerous existing solutions, each with its own challenges:
 
-* Wired telephone is a reliable solution, however poses a significant investment due to the above challenges, plus it is easily damaged in confined or gravel passages.
+* Wired telephone is a reliable solution, however poses a significant investment due to the above challenges, plus it is easily damaged in confined passages, boulder chokes, gravel etc.
 * [Through-the-earth radio communications](https://en.wikipedia.org/wiki/Through-the-earth_mine_communications) using very low radio frequencies (HeyPhone, Nikola, CaveLink) are the most popular _ad-hoc_ communications solution during cave rescue or expeditions . Obtaining a reliable link at depths below hundreds of meters however is a lottery as many factors from geology to weather impact attenuation even at  low frequencies.
 * Underground communication links based on radio repeaters was discussed at least since 2014[^1]. _Sybet_ came up with industrial solution [SPELLCOM](https://sybet.eu/batnode/)  using radio repeaters to relay voice communications over underground cavities.
 
@@ -102,19 +102,38 @@ Other parts:
 
 # Flashing firmware
 
-Make sure you have **the same version** on all devices. There are ocassional incompatibilities between even minor
+There's two firmwares now available for testing:
-versions. I usually target for the latest _beta_ release. Generally, new releases ship many bugfixes so it's
+
+* Mainline Meshtastic firmware, which is stable and feature-rich but has the
+  hop limit hardcoded to 7 nodes
+* Vangelis firmware, which is experimantal but has the hop limit removed
+
+**Note:** if you get weird errors, timeouts etc first check the USB cable connection, which may be especially likely if mud or dust get into your external USB port. Try to remove and reinsert the cable, blow with compressed air a few times. Last resort, you need to remove the board from the 3D printed case and it should always work.
+
+## Flashing Meshtastic firmware
+
+Make sure you have **the same version** on all devices. There are ocassional incompatibilities between even minor versions. I usually target for the latest _beta_ release. Generally, new releases ship many bugfixes so it's
 worth keeping them up to date.
 
-Connect your device over USB cable and use [Meshtastic Web Flasher](https://flasher.meshtastic.org)
+Connect your device over USB cable and use [Meshtastic Web Flasher](https://flasher.meshtastic.org) to download the right firmware UF2 file and, which is especially useful, switch the board into bootloader (DFU) mode. This saves you opening the case and pulling out the board only to press the reset button twice. Please note that if your board was already flashed with firmware <2.2, it won't work and you need to use the button.
-to download the right firmware UF2 file and, which is especially useful, switch the board into bootloader (DFU) mode.
-This saves you opening the case and pulling out the board only to press the reset button twice. Please note that
-if your board was already flashed with firmware <2.2, it won't work and you need to use the button.
 
-When the board goes into DFU mode, it becomes visible as an USB storage device to the computer and you will
+When the board goes into DFU mode, it becomes visible as an USB storage device to the computer and you will see a new RAK4631 folder on your computer, where you simply copy the UF2 file. If you don't, power cycle, reconnect
-see a new RAK4631 folder on your computer, where you simply copy the UF2 file. If you don't, power cycle, reconnect
 and try the DFU mode again.
 
+## Vangelish firmware
+
+You can either:
+
+* Clone the [vangelis-firmware](https://github.com/semper-ad-fundum/vangelis-firmware.git) and build using PlatformIO
+* Download the built [UF2 firmware](https://github.com/semper-ad-fundum/vangelis-firmware/releases/tag/v1.0.0) and copy it to the device using the above instructions (not tested)
+
+Command to flash firmware built using PlatformIO is:
+
+```
+platformio run --environment rak4631 --target upload
+```
+Advantage of PlatformIO is that it will put your firmware in DFU mode automatically.
+
 # Configure
 
 You can't configure a headless Meshtastic device over Bluetooth alone, so you will need the Python CLI or Web Client. See [Meshtastic initial configuration guide](https://meshtastic.org/docs/getting-started/initial-config/)