docs: x4xx: Update information on CPLD updating

1 files changed, 19 insertions, 0 deletions

diff --git a/host/docs/zbx.dox b/host/docs/zbx.dox
index 3d6a3e527..727a00b7d 100644
--- a/host/docs/zbx.dox
+++ b/host/docs/zbx.dox
@@ -420,6 +420,10 @@ The "software defined" mode can be enabled for the DSA tables by using the
 
 \section zbx_updating_cpld Updating the ZBX CPLD
 
+Note: You may need to update the ZBX CPLD after updating filesystems. If an
+update is required, MPM will fail to initialize, and provide a corresponding
+error message.
+
 If you need to update the ZBX CPLD, you can do so by running the following command
 on the device:
 
@@ -436,6 +440,21 @@ By default, the `cpld-zbx.rpd` file will be provided at
 `/lib/firmware/ni/cpld-zbx.rpd`. Note that after downloading the ZBX CPLD, you
 will need to completely shut down and power-cycle the device.
 
+If you are updating the image during a filesystem update, i.e., after installing
+the new filesystem with Mender, but before rebooting, you will need to mount
+the new filesystem first and copy the image over:
+
+    mkdir /mnt/other
+    mount /dev/mmcblk0p3 /mnt/other
+    cp /mnt/other/lib/firmware/ni/cpld-zbx.rpd ~
+    umount /mnt/other
+
+Note that the other filesystem may be either `/dev/mmcblk0p2` or `/dev/mmcblk0p3`.
+You can now update to the new CPLD image:
+
+    zbx_update_cpld --file=~/cpld-zbx.rpd
+
+
 \subsection zbx_updating_cpld_details CPLD Programming: Details
 
 Read this section if you want to create your own ZBX CPLD image, or require more