Since firmware version 1.8.18, the TRMNL X offers a diagnostic screen, accessible through the touchbar menu system. Pressing the middle of the touchbar (below the screen) activates the menu:
Select Settings... to proceed:
Select Diagnostics... to display the data:
Summary of Each Row
Firmware: version currently installed, including the commit.
Friendly ID: Unique identifier for pairing the device to an account. Reset when unpaired from trmnl.com account.
Battery: 3%-100% charge will range between 3.5v and 4.3v, however the battery module reports the percentage.
Battery Temperature: Should be close to the ambient room temperature since the device sleeps most of the time.
Wi-Fi Network/Band: SSID and Band used
Wi-Fi Signal: Ranges from -30dBm to -90dBm typically; the closer to 0, the better. -50dBm to -67dBm is most common. Anything less than that (e.g. -80dBm) is a poor signal and will create higher battery drain and failed screen downloads.
Refresh: How long it is going to sleep.
Server: https://trmnl.app is most common unless you are using BYOS.
Panel: Software reported EPD version, if detected/available.
Free Memory:
heapis where the ESP32 chip "OS" is kept, whilePSRAMis for screen storage and other things.