2MS DATV from Raspberry Pi

[G8GKQ]

As described in CQ-TV, Evariste F5OEO has made some updates to the rpidatv software, and I have been testing it for incorporation into a transmitter. It will now output I and Q signals at up to 2 MS which can be passed to a DigiLite-style modulator.

Here are some tips on how to make it work on an RPi3:

• First download the March 2016 release of Raspbian Jessie Lite from here http://downloads.raspberrypi.org/raspbi ... 016-03-18/. Evariste has not tested with later Raspbian images.
• Unzip the image and then transfer it to an SD Card using Win32diskimager
• Power up the Pi with a network connection, keyboard and hdmi display
• Log in (pi/raspberry), and type raspi-config to open the configuration tool. Expand the file system to the whole disk, and enable the camera.
• Exit raspi-config and type ifconfig. Make a note of the Pi's IP address. Type sudo shutdown now.
• Power-off, connect the camera, disconnect the keyboard and display and reboot.
• From another PC open a terminal (use Putty on a windows PC) and log in
• Following the instructions at https://github.com/F5OEO/rpidatv cut and paste the following code in:

  Code: Select all

  wget https://raw.githubusercontent.com/F5OEO/rpidatv/master/install.sh
  chmod +x install.sh
  ./install.sh

• Type sudo reboot now, log in again and then start the software by typing: ./rpidatv/scripts/gbmenu.sh

You can now explore the menu options and play.

Evariste has only tested on an RPi2, I have been using an RPi3. I succeeded in generating a direct RF output (from GPIO pin 32) on 437 MHz at 333KS using the on-board camera as the source; it would not work reliably at higher SRs. The big win for me is that I could feed the I and Q signals from pins 32 and 33 directly into the LC filter on my old DigiLite modulator and generate a 2MS QPSK H264 DVB-S signal from the on-board camera. Some adjustment of the bias is required as the I and Q signals from the Pi are 3.3v, not 5 v as provided by the DigiLite encoder.

I have not been so successful with other picture sources and am trying to pin-down the problems and report them back to Evariste, but there is lots of potential here. I will post here with progress reports. Thanks to Evariste for his work on this project.

Dave G8GKQ

[g0mjw]

There is quite a bit more to it that indicated below if you want to use the Adafruit TFT (which by the way does not work with the gui yet but does give you a console) as you need to download their Jessie image. Note there are several different TFTs and you need to have the right setup for the one you have.

The images are to be found at https://adafruit-download.s3.amazonaws. ... TFT35r.zip or https://s3.amazonaws.com/adafruit-raspb ... r-lite.zip

Follow the instructions on the adafruit webpage https://learn.adafruit.com/adafruit-pit ... i/overview or https://learn.adafruit.com/adafruit-pit ... i/overview

Don't then update the kernel image as it will overwrite the adafruit TFT kernel. This means editing the install script to comment out the rpi-update commands.

#rpi-update to get latest firmware
#sudo rpi-update

Also, I have had little success with the original PI. I am assuming it is no longer supported and as Evariste hasn't got one it is unlikely to ever be, so I have given up and will probably take it to bits to reuse the parts. I will see what I can do to get the digilite boards (older and newer) which do not fit on any of the new PIs, but connected to one of the newer PIs which are a good deal faster as I think they only need a few lines Power, I, Q and I2C for the LO.

Mike

[arthur21]

I have also installed F5OEO's latest Rpidatv and have managed to get it work on a Rpi3 taking the Q signal from GPIO13 pin 33 but I have not managed to get the Q signal to appear on any of the low number pins to appear on the older Rpi with just 26 pins maybe this is not possible.

The new software now allows me to transmit video from an EasyCap dongle but only in monochrome. I suspect the EasyCap settings may need some adjustment for PAL. Has anyone succeeded in getting colour.

73 Arthur
G4CPE

[g8gtz]

Hi Arthur

The monochrome sounds like the eazicap using the S video input - rather than work out how to fix the config, I've found it's easier to go in on the S video plug and just short the Luma / Chroma pins together and join them to composite input.

Pi 3 on order The bold plan is to try and pull this all together to produce an easy beginners project with full documentation etc...

Noel - G8GTZ

[G8GKQ]

Hi Arthur

My EasyCap gives negative colour. Not sure about the luminance! Have spent some time investigating, but no progress yet.

Dave, G8GKQ

[f5oeo]

Quick note : about monochrome : easycap is usually in NTSC mode by default.
I run this little script before launching rpidatv :
v4l2-ctl -d /dev/video0 --set-input=0
v4l2-ctl -d /dev/video0 --set-standard=6

This turns easycap in composite input and PAL.
If you need other configuration check it with v4l2-ctl

About Pi models which working : I want to support all models. Latest models (since B+) have 40 pins which is easier to get I and Q directly on header. On the 26 pins model (PI B), you have to solder at least on wire to get the Q pin. You can find surely how in digithin documentation. Need to add something on the wiki !

About TFT : I include in the image some drivers, but difficult to include "ALL" the drivers as soon as to be sure it is working I have to buy them all ! A solution could be to have remotely acess to rasberry and then add it.
Right now only Waveshare driver 3.5", and Tontec drivers are supported (MZ61581)

Need maybe to add adafruit one as it is quiet popular ! Think to have one somewhere in the shack !

About Image : even image build is now automatic, I prefere to publish image less often but more "reliable"'. If you want to be up-to-date : follow procedure on https://github.com/F5OEO/rpidatv

73's Evariste F5OEO

[arthur21]

Hi Evariste

I had completely forgotten about adding the wire on the older Rpi and of course it works OK.
The grabber does not run very smooth on the older Pi suspect it is lack of computer power, but fine for still pictures.
On the Rpi3 results are very good. I have yet to try the commands to set the grabber into PAL mode but I hope to do that soon.
Many thanks.

73 Arthur
G4CPE

[G8GKQ]

Hi All

I'm still struggling with my capture device. Here's the picture that I get

EasyCap Problem.JPG (147.33 KiB) Viewed 6723 times

and this is the device configuration:

Code: Select all

pi@raspberrypi:~ $ v4l2-ctl -d /dev/video0 --set-standard=6
Standard set to 00000007
pi@raspberrypi:~ $ v4l2-ctl -d0 --all
Driver Info (not using libv4l2):
        Driver name   : usbtv
        Card type     : usbtv
        Bus info      : usb-3f980000.usb-1.2
        Driver version: 4.4.23
        Capabilities  : 0x85200001
                Video Capture
                Read/Write
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps   : 0x05200001
                Video Capture
                Read/Write
                Streaming
                Extended Pix Format
Priority: 2
Video input : 0 (Composite: ok)
Video Standard = 0x000000ff
        PAL-B/B1/G/H/I/D/D1/K
Format Video Capture:
        Width/Height  : 720/576
        Pixel Format  : 'YUYV'
        Field         : Interlaced
        Bytes per Line: 1440
        Size Image    : 829440
        Colorspace    : Broadcast NTSC/PAL (SMPTE170M/ITU601)
        Flags         :
Streaming Parameters Video Capture:
        Frames per second: 25.000 (25/1)
        Read buffers     : 2

I've tried both inputs, and it does work on Win10 with VLC. Maybe it's incompatible - or does it just need a configuration change?

Dave
G8GKQ

[arthur21]

Hi Dave
I have two identical looking EasyCap dongles.one gives me exactly the result you are getting but the other one gives a perfect monochrome picture.
Both of these devices work correctly in Windows programs.
I have not yet managed to sort out how to run the script to put the grabber into PAL mode before Rpidatv runs. My computer skills are poor but it is a challenge and I will keep trying and report the results.

Arthur G4CPE

[g0mjw]

About Pi models which working : I want to support all models. Latest models (since B+) have 40 pins which is easier to get I and Q directly on header. On the 26 pins model (PI B), you have to solder at least on wire to get the Q pin. You can find surely how in digithin documentation. Need to add something on the wiki !

73's Evariste F5OEO

A quick test using a spectrum analyser shows that the original PI does work, but the modulation only appears for about a second or two before stopping. So something isn't right. Once I managed to capture an image - which was valid, so it starts up OK but then stops.

I think we need a new Digithin as a standalone board (with mounting holes) that does not sit on the header and includes the LO and RF filtering. This would mean it would work with any IQ source and it would be easier for beginners if it didn't need to be constrained to the PI format. Maybe also better for RF stability if it fitted into a standard screened box.

Rather then try to stack it, one of these Ebay 131811038036 or 231847860514 may be useful.


Mike