Previously I setup a CC2531 as a Zigbee coordinator for my home automation. This has turned out to be a good move, with the 4 gang wireless switch being particularly useful. However the range of the CC2531 is fairly poor; it has a simple PCB antenna. It’s also a very basic device. I set about trying to improve the range and scalability and settled upon a CC2538 + CC2592 device, which feature an MMCX antenna connector. This device also has the advantage that it’s ARM based, which I’m hopeful means I might be able to build some firmware myself using a standard GCC toolchain.

For now I fetched the JetHome firmware from https://github.com/jethome-ru/zigbee-firmware/tree/master/ti/coordinator/cc2538_cc2592 (JH_2538_2592_ZNP_UART_20211222.hex) - while it’s possible to do USB directly with the CC2538 my board doesn’t have those bits so going the external USB UART route is easier.

The device had some existing firmware on it, so I needed to erase this to force a drop into the boot loader. That means soldering up the JTAG pins and hooking it up to my Bus Pirate for OpenOCD goodness.

OpenOCD config 
source [find interface/buspirate.cfg]

buspirate_port /dev/ttyUSB1
buspirate_mode normal
buspirate_vreg 1
buspirate_pullup 0

transport select jtag

source [find target/cc2538.cfg]
Steps to erase 
$ telnet localhost 4444
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Open On-Chip Debugger
> mww 0x400D300C 0x7F800
> mww 0x400D3008 0x0205
> shutdown
shutdown command invoked
Connection closed by foreign host.

At that point I can switch to the UART connection (on PA0 + PA1) and flash using cc2538-bsl:

$ git clone https://github.com/JelmerT/cc2538-bsl.git
$ cc2538-bsl/cc2538-bsl.py -p /dev/ttyUSB1 -e -w -v ~/JH_2538_2592_ZNP_UART_20211222.hex
Opening port /dev/ttyUSB1, baud 500000
Reading data from /home/noodles/JH_2538_2592_ZNP_UART_20211222.hex
Firmware file: Intel Hex
Connecting to target...
CC2538 PG2.0: 512KB Flash, 32KB SRAM, CCFG at 0x0027FFD4
Primary IEEE Address: 00:12:4B:00:22:22:22:22
    Performing mass erase
Erasing 524288 bytes starting at address 0x00200000
    Erase done
Writing 524256 bytes starting at address 0x00200000
Write 232 bytes at 0x0027FEF88
    Write done
Verifying by comparing CRC32 calculations.
    Verified (match: 0x74f2b0a1)

I then wanted to migrate from the old device to the new without having to repair everything. So I shut down Home Assistant and backed up the CC2531 network information using zigpy-znp (which is already installed for Home Assistant):

python3 -m zigpy_znp.tools.network_backup /dev/zigbee > cc2531-network.json

I copied the backup to cc2538-network.json and modified the coordinator_ieee to be the new device’s MAC address (rather than end up with 2 devices claiming the same MAC if/when I reuse the CC2531) and did:

python3 -m zigpy_znp.tools.network_restore --input cc2538-network.json /dev/ttyUSB1

The old CC2531 needed unplugged first, otherwise I got an RuntimeError: Network formation refused, RF environment is likely too noisy. Temporarily unscrew the antenna or shield the coordinator with metal until a network is formed. error.

After that I updated my udev rules to map the CC2538 to /dev/zigbee and restarted Home Assistant. To my surprise it came up and detected the existing devices without any extra effort on my part. However that resulted in 2 coordinators being shown in the visualisation, with the old one turning up as unk_manufacturer. Fixing that involved editing /etc/homeassistant/.storage/core.device_registry and removing the entry which had the old MAC address, removing the device entry in /etc/homeassistant/.storage/zha.storage for the old MAC and then finally firing up sqlite to modify the Zigbee database:

$ sqlite3 /etc/homeassistant/zigbee.db
SQLite version 3.34.1 2021-01-20 14:10:07
Enter ".help" for usage hints.
sqlite> DELETE FROM devices_v6 WHERE ieee = '00:12:4b:00:11:11:11:11';
sqlite> DELETE FROM endpoints_v6 WHERE ieee = '00:12:4b:00:11:11:11:11';
sqlite> DELETE FROM in_clusters_v6 WHERE ieee = '00:12:4b:00:11:11:11:11';
sqlite> DELETE FROM neighbors_v6 WHERE ieee = '00:12:4b:00:11:11:11:11' OR device_ieee = '00:12:4b:00:11:11:11:11';
sqlite> DELETE FROM node_descriptors_v6 WHERE ieee = '00:12:4b:00:11:11:11:11';
sqlite> DELETE FROM out_clusters_v6 WHERE ieee = '00:12:4b:00:11:11:11:11';
sqlite> .quit

So far it all seems a bit happier than with the CC2531; I’ve been able to pair a light bulb that was previously detected but would not integrate, which suggests the range is improved.

(This post another in the set of “things I should write down so I can just grep my own website when I forget what I did to do foo”.)