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How to build the P44-TTNGW firmware image based on LEDE


prerequisites for OpenWrt on Linux

Details see official OpenWrt instructions.

Usually the following is sufficient:

  • sudo apt-get install git-core build-essential libssl-dev libncurses5-dev unzip gawk zlib1g-dev

Additionally, we need quilt to patch the OpenWrt tree with p44b before running make for the first time (which will build quilt), so we just install it:

  • sudo apt-get install quilt

prerequisites for OpenWrt on macOS

  1. OpenWrt needs a case sensitive file system, but macOS by default has a case insensitive file system. So OpenWrt needs to be put on a volume with case sensitive file system.

    On macOS before 10.13, you can create a sparse image of ~20GB with Disk Utility.

    With macOS 10.13 and later, the APFS file system allows creating extra volumes without partitioning or reserving any space - this is much better than a disk image (Disk Utility -> Edit -> Add APFS volume...)

  2. XCode needs to be installed

  3. Some utilities are needed from homebrew

    • install brew as described here
    • brew tap homebrew/dupes
    • brew install coreutils findutils gawk gnu-getopt gnu-tar grep wget quilt xz
    • brew ln gnu-getopt --force

Also see OpenWrt Quick Image Building docs for general info about OpenWrt bootstrap.

Get OpenWrt (formerly LEDE, formerly OpenWrt)

Assuming that you've created and mounted a case sensitive volume named CaseSens already (macOS case, for Linux just use any directory of your choice):

cd /Volumes/CaseSens
git clone -o -b openwrt-18.06 openwrt

Get the p44build script

Note: this is a script that helps managing differently configured OpenWrt targets on top of an unpolluted OpenWrt original tree.

git clone -o github

Start working with OpenWrt

Go to the directory where you checked out OpenWrt and p44build (/Volumes/CaseSens on macOS according to the steps above). Then:

cd openwrt
git checkout -b p44ttngw v18.06.2

Configure the extra feeds we need

# do NOT change feeds.conf.default - custom changes belong into feeds.conf!
cp feeds.conf.default feeds.conf
echo "src-git plan44;master" >>feeds.conf
echo "src-git onion" >>feeds.conf

./scripts/feeds update -a

optionally: Unshallow plan44 feed to be able to work with tools like GitX in it

OpenWrt clones only a shallow (no history) copy of the feed repository. This saves space, but limits git operations (and crashes tools like GitX). The following steps convert the feed into a regular repository:

pushd feeds/plan44
git fetch --unshallow

Initialize p44b(uild) for p44ttngw

Direct p44b to the information that will control everything

../p44build/p44b init feeds/${TARGET_CFG_PACKAGE}/p44build

Prepare (patch) the OpenWrt tree for p44ttngw

./p44b prepare

Note: My standard setup disables any password based login by default, by providing a modified shadow file in files/etc/shadow. If you want the standard OpenWrt default of no initial password, then delete this extra file now:

rm files/etc/shadow

Install needed packages from feeds

only install (= make ready for OpenWrt to potentially build at all) those packages that were recorded present at last './p44b save':

./p44b instpkg

or just install all packages from all feeds:

./scripts/feeds install -a

Some tweaks apparently needed (for now)

  1. If python/python3 package is installed, make will try to host-compile it and fail on macOS. As we don't need python at all, just make sure those packages are not installed:

    • ./scripts/feeds uninstall python
    • ./scripts/feeds uninstall python3

Configure OpenWrt for the target platform

# shows all possible targets, currently only Omega2
./p44b target

# select the target
./p44b target p44ttngw-omega2

optionally: Inspect/change config to add extra features

make menuconfig

Build P44-TTNGW image

# or, if you have multiple CPU cores you want to use (3, here)
# to speed up things, allow parallelizing jobs:
make -j 3

Note: when doing this for the first time, it takes a looooong time (hours). This is because initial LEDE build involves creating the compiler toolchain, and the complete linux kernel and tools. Subsequent builds will be faster.

Use the firmware to run a TTN gateway

Prepare the hardware

Of course, to actually get a working TTN gateway, you also need to connect a LoRa concentrator to the SPI bus. I use a RAK831, connected as follows:

Function Omega(2) Dock Omega2 RAK831
+5V 5V 5V 1
SCK 7 SPI_CK(7) 18
MISO 12 (or 9) MISO(9) 17
MOSI 8 MOSI(8) 16
CS1 6 CS1(6) 15

Flash the firmware image to the Omega2

If everything went well, the LEDE build process will have produced a ready-to-flash firmware image in bin/targets/ramips/mt76x8. You can now send this to the Omega2 and flash it.

# specify the IP address of your Omega2 here

# copy FW image to the Omega2
scp -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no bin/targets/ramips/mt7688/p44ttngw-*-ramips-mt7688-omega2-squashfs-sysupgrade.bin root@${TARGET_HOST}:/tmp

# login to the Omega2
ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no root@${TARGET_HOST}

# on the Omega2, flash the new firmware image
cd /tmp
sysupgrade -n p44ttngw-*.bin

After that, Omega reboots and is now a TTN gateway :-)

Note: The image's default config has WiFi enabled including an access point named P44TTNGW. To disable Wifi, or to connect the gateway to a WiFi AP, edit /etc/config/wireless accordingly (especially the option disabled and ssid/key).

Configure the gateway

For now (first rough version of this package), the gateway LoRa config is completely static except for the gateway EUI (which is calculated from the Omega2 MAC address).

You can edit /etc/lora/local_conf.json to add your gateway name/description. But do not change the ##GATEWAY_EUI##, this is a placeholder for the MAC-derived EUI!

start, stop, logs, tools

packet_forwarder is under runit control, so you can stop and start it (after boot, it starts automatically) and see current status from command line:

sv stop p44ttngw
sv start p44ttngw
sv status p44ttngw

Current log is in /var/log/p44ttngw/current, to have it displayed live:

tail -F /var/log/p44ttngw/current

The tools to low-level test SPI communication with the concentrator (util_*, test_loragw_*) are in /root/lora. Don't forget to sv stop p44ttngw before trying these tools.

Finally, but optionally: save your build's config, feeds, versions

On the build machine:

./p44b save

This records the precise details of this build into feeds/plan44/p44ttngw-config/p44build, in particular the LEDE tree's SHA and .config as well as the SHAs of the feeds used. The idea is that this can be committed back into the p44ttngw-config package, as kind of a "head" record for this very p44ttngw firmware build, and allows to go back to this point later, even if the LEDE tree was used to build other firmware images in between (in fact, exactly that is the very purpose of p44b - the ability to work and switch between different firmware projects in a single LEDE tree)

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