> For the complete documentation index, see [llms.txt](https://graygzou.gitbook.io/how-to/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://graygzou.gitbook.io/how-to/others/raspberrypi.md).

# Raspberry Pi infos

## Having troubles with your tv screen ?

1\) Run the following commands to know what's going on with your screen and the raspberry pi

```
tvservice -s (or --status) # get HDMI status : will tell you what your current HDMI mode is.
tvservice -m CEA (or --modes=CEA) # get supported modes for CEA : will tell you the "CEA modes" available. (hdmi group 1)
tvservice -m DMT (or --modes=DMT) # get supported modes for DMT : will tell you the "DMT modes" available. (hdmi group 2)
```

### CEA vs DMT

* CEA modes are intended for TV, they include plenty of interlaced and progressive modes, 

  usually with 25/50/100Hz (PAL) or 30/60/120Hz (NTSC) 

  frame rates and TV resolutions of 288/480/576/720/1080 scan lines. 
* DMT modes are intended for computer monitors, therefore there are none of the interlaced modes, 

  the resolutions are 640/720/800/1024/1280 and 

  the frame rates are compatible with the computer monitors, something like 60/70/75/80/85/120Hz.

### /boot/config.sys

By modifying this file, you can hard code display data for the raspberry pi.

```
sudo nano /boot/config.sys
```

For example, you can change :

```
sdtv_aspect=3
```

in order to have 16:9 aspect and

```
hdmi_safe=1.
```

to force getting a picture on HDMI for a default "safe" mode.

### Sources

* <https://www.raspberrypi.org/forums/viewtopic.php?t=72871>
* <https://www.raspberrypi.org/forums/viewtopic.php?t=52309>
* <https://raspberrypi.stackexchange.com/questions/7332/what-is-the-difference-between-cea-and-dmt>
* <https://github.com/raspberrypi/userland/tree/master/host_applications/linux/apps/tvservice>