TABLE OF CONTENTS
DAKboard OS devices, whether purchased from our Shop, one of our Resellers, or done as a DIY project all use HDMI as their method to connect to the display. This article intends to cover the various HDMI connections you will find on Orange Pi and Raspberry Pi computers we use and you can buy and how they play an integral part of your complete Display package.
DAKboard OS and HDMI:
The DAKboard OS not only uses the capabilities of HDMI to send and receive Audio and Video, but it also uses these lines of communication to gather information on your Monitor/TV's make and model. Furthermore, we utilize the CEC capabilities of most modern TVs and Monitors to allow you to turn on and off your Monitor/TV using the DAKBoard device's built-in On/Off (Sleep) Schedule.
Because we use advanced features such as CEC, when a DAKboard OS device first boots up, it reaches out to the connected Monitor/TV to confirm it is using the HDMI connection and waits for a response. Sometimes it fails to get this response and reacts by rebooting itself to try and establish communication. If your DAKboard OS device is boot looping, only going to the DAKboard loading page, or a rainbow-colored screen repeatedly, this means that your DAKboard is not getting the response from your Monitor/TV.
This can be a sign that either your HDMI Cable is bad or your connection to the CPU and Monitor/TV is loose. If the cable is bad it will need to be replaced if the connection is loose, you can correct this by simply unplugging the power to your DAKboard CPU, unplugging both the HDMI connection on the CPU and the Monitor/TV, then plugging the HDMI cable back in making sure the connection is sound on both ends. Then simply plug the power back in and your device will start up.
HDMI connections of the CPUs v3 and v4:
In our current models, the v3 is powered by the Orange Pi 3 LTS, and the v4 is powered by the Raspberry Pi 4B. As seen below, the v3 has a single standard HDMI output:
While the v4 supports Dual Micro HDMI outputs.
Though the v4 has two HDMIs out, they do not function independently. This means that the Secondary HDMI output, the one furthest from the power supply, is just a mirrored copy of the Primary HDMI output. So you can hook the CPU v4 to multiple monitors, but it will show the same Screen on both monitors.
Below is a matrix of what is supported by these HDMI Outputs:
| Device | Supported Output | Video | Audio | CEC | Individual Screen | Resolutions |
| CPU v3 | HDMI | Yes | Yes | Yes | Yes | 2k UW, 4k, 1080p, 720p |
| CPU v4 | Primary Micro HDMI | Yes | Yes | Yes | Yes | 2k & HD UW, 4k, 1080p, 720p |
| CPU v4 | Secondary Micro HDMI | Yes | Yes | Yes | No | 2k & HD UW, 4k, 1080p, 720p |
NOTE: As of version 4.01 and above, the DAKboard CPU v4 will support audio through both the Primary and Secondary HDMI outputs as well as through the auxiliary headphone output. If you are running an older version, 3.54 and below, you will need to upgrade to get these added features. You can upgrade to the latest version of the OS by following the steps in our article Raspberry Pi - Download and Install the DAKboard OS.
Frequently Asked Questions:
Can you see two different Screens or photos when using the Dual output on the CPU v4?
No. This is because the secondary output is mirroring the primary output. Both will show the same screen at the same time.
Does the Secondary HDMI output support audio?
For versions 4.02 and above, the Secondary HDMI output now supports Audio. For version 3.54 and below, this was not supported.
Can DAKboard CPUs be converted to work on other input types?
No. The DAKboard CPU requires the use of HDMI signals to function properly. Converting the HDMI signal to any other input type (like DVI, Display Port, VGA, or RCA inputs) will cause the CPU to fail to function or behave in unpredictable ways. You should only use monitors/TVs with HDMI inputs and should use monitors/TVs that support CEC (Consumer Electronic Controls) to be able to take advantage of all the DAKboards OS functionality.
What does it mean when the TV Shows No HDMI Signal?
This message would be coming from your TV or Monitor not from the DAKboard OS. This could be caused if the wrong HDMI input is selected on your TV or Monitor, or the HDMI signal is not being sent or received. Double check you have the correct input selected on your TV or Monitor, make sure the CPU's power is on, and if you are still not seeing the image, try unplugging and plugging the HDMI cable back in on both the CPU and TV, or replacing the HDMI cable.