Tachyon requires 3A to run (and up to 5A if you hand more items off its peripheral busses). I have 100% seen similar issues when the power supply wasn’t enough - debugging this from a user side is tough as the action is basically “no display” unless you flash in headless mode and then dump out the USB input voltages.
Still working on the virtual display patch - I personally dislike the idea that this is needed, but it does appear to be a root issue of GDM in 20.04 timelines so I think we’ll have to just get it working and move on.
Thanks Nick. The issue seems to be when using the Tachyon official power adapter and not having enough power when using USB C for DP Alt mode. Strange that even more power is needed to drive USB-C to HDMI over DP Alt. In hindsight it may have been good to include mini HDMI port like Raspberry PI and not depend on the same USB-C port for power and DP Alt or provide both USB C with DP Alt and bidirectional power.
This is interesting and made me think of another variable I didn’t initially consider.
What battery are people using when they experience the different display ‘failure modes’.
When I posted my original thread I had only used the add-on 3-cell LiPo that I ordered along with my Tachyon. With it I only get HDMI output at boot (cold boot or warm boot) when I have no external power source connected at all. Only after I get the HDMI display output can I then connect the external power supply to the USB hub to begin charging the battery. But, in the case where I have the external power supply connected to the hub at boot time and I get no display (timing issue that Nick described) restarting gdm gets my display going every time.
Now, I just tested with the single-cell LiPo that was included with the Tachyon and my experience mirrors other reports in that I get no HDMI output (external power supply connected or not), but as with the case using the 3-cell LiPo restarting gdm still gets my HDMI output going. So perhaps it is a combination of external power supply and the output capacity of the LiPo we are using that plays into all of this as well.
I was initially was using the single cell lipo and had display issues until I started using the 60W powered USB C dock. I am currently using the 3 cell lipo and seems more stable, but I now just RDP into the Tachyon and leave USB-C dock disconnected from the Tachyon.
I’ve been using the desktop version for several days and had been doing some sensor / SSD1306 display tests, and had done several apt updates/upgrades without any issues. Cellular connectivity and WiFi have been fine. Overall, the system has been pretty stable. However, this afternoon I decided to shutdown and restart the Tachyon.
Now, I’m unable to bring up the HDMI display unless I run systemctl restart gdm. The HDMI comes up everytime but I’m unable to run Terminal (or Vim, HTop) from the desktop. I’m able run all the other desktop applications. Weird!
I’ve repeated the process several times and get the same behaviour.
The following setup & power sequence seems to work most of the time again.
keyboard, mouse & HDMI connected to a 100W PD UGREEN Revodok USB C Hub 6-in-1
240W USB C to USB C cable connected to Tachyon USB-C 1
power down Tachyon
unplug both USB-C cable from USB-C 1 and battery (1-cell or 3-cells)
re-connect battery, red led on
reconnect USB-C cable
Tachyon goes from green to breathing cyan, cellular & W-Fi connectivity, HDMI display ON
Reset Tachyon via button, red led → green → cyan, HDMI display ON
Reboot from a remote session, red led; press the Tachyon reset button, HDMI display ON
Of course, restarting gdm service works every time in bringing up the HDMI display.
The Terminal app not launching was a different issue to do with Python. A few days back, I had upgraded Python from Ubuntu 20.04 default 3.8 to 3.10. I didn’t realize that /usr/bin/gnome-terminal uses python3.8.
Used sudo update-alternatives --config python to change python3 to point back to python3.8.
I just received my Tachyon today and, after following the installation guide (https://developer.particle.io/tachyon/setup/install-setup), I'm experiencing the same issue after setting up the desktop environment — no video output at all.
In my case, I had my monitor connected via HDMI to the Ugreen hub that came with the Tachyon (https://developer.particle.io/tachyon/accessories/usb-c-accessories#). I also had a mouse and keyboard connected via USB, and the recommended 35W USB-C power supply provided by Particle plugged into the hub, as instructed in the installation guide. The 3-cell battery was also connected to the battery connector.
In this setup, the RGB LED was breathing cyan, and I was able to connect to the Tachyon via the terminal in the Particle Console. However, the monitor was not receiving any video signal.
I then discovered that unplugging the power supply from the USB-C hub resolved the video output issue — the display started working. However, I’m unable to charge the battery either through the USB-C hub or the USB-C2 port on the Tachyon. Using my 62W Mac's USB-C power supply results in the same issue.
Interesting. I am not seeing that issue. I have three cell battery connected and connecting to USB C port #1 to the dock to charge and video. Are you using port #1 since that is only one that does DP-Alt for video and bidirectional power.
@terracode Thanks for your answer! Yes I am aware of that and I am using usbc1 to connect the usbc hub.
Previously, I mentioned that if I boot the tachyon using only battery power, the hdmi monitor receives video correctly over the usbc hub connected to the usbc1.Now, I've discovered something new: If I plug in the power adapter after the tachyon has already booted on battery, the video output continues to work properly, and the battery starts charging as expected, so I can charge my 3-cell battery. But this is still an abnormal behaviuor.
I hope Particle resolves the dilemma of having to connect the battery to boot the Tachyon as well as the issue you described. I would like to power it off without having to disconnect battery each time. During development I would just like to use power from the dock without needing to worry about battery connection.
I had my Tachyon setup with a case using a USB-C extension cable that came with it and none of these suggestions worked. I took it out of the case and plugged the hub directly into USB 1 and was able to get an HDMI display after “systemctl restart gdm”. I then did a reboot from within the GUI and it was persistent, desktop came up again.
As marked in the documentation, the included extension cable is USB2. You cannot run display port alt mode on USB2 cabling. I havent ordered/received one yet but I have found ADT link make a few USB 3.2 2x2 extensions that are similar in formfactor and I would like to try one of those out and see if it fits in the case to provide an interface capable of being headed.
Add me to the list of folks fighting this issue… I have had some success with running ‘sudo systemctl restart gdm3’ from ssh to get the display working after reboot. I also did some testing by disconnecting the USB-c power as noted by @enigmaturing above, and booting only with the single battery bank provided with the tachyon. I have had 100% success with hdmi output using that boot approach on several different monitors. I can also confirm that the battery does begin charging when you plug in USB power after the desktop is booted.
Unfortunately, I am seeing an issue that appears to occur over time, likely when the monitor ‘goes to sleep’ after inactivity for a long period of time. In that case, running ‘sudo systemctl restart gdm3’ or ‘sudo systemctl restart init_display.service’ makes the monitor appear to be active (Based on the monitor status lights') but only shows a blank black desktop (not even the purple background or login prompt). To date, only rebooting restores the HDMI output.
I’m not sure of the exact timing, as this doesn’t happen every time the monitor goes to sleep, but happens when it is inactive over several days. This does limit the usefulness of the desktop environment, as it results in restarting the environment if you haven’t actively interacted with the desktop for a while.
I have the exact same problem. After a long period of inactivity (seems like a couple of days), the Tachyon screen will NOT wake up and nothing I do via remote terminal will bring the video back except rebooting the unit.
Hi, there's a definitive solution. I have the same problem, and I can't get the HDMI to work after trying everything. It worked the first time, but after turning it off, the HDMI no longer works.
I’m in the same boat sometimes it works sometimes it doesn’t, i have two usb-c HP multi-adapters (different models all of them +80W power) and i need to do a roulette every-time.
I have similar experiences, sometimes coming back hours later (desktop mode) the device wouldn’t activate the hdmi from sleep. I just rebooted to fix it, but that was less than ideal.
Other times moving the USB HID input devices would wake the Tachyon and display turn back on.
If I plug in the power adapter after the tachyon has already booted on battery, the video output continues to work properly, and the battery starts charging as expected, so I can charge my 3-cell battery. But this is still an abnormal behaviuor.