Hardware-only Transmit Switching

As of software version 201710080 (not yet released), the Portsdown transmitter can be configured so that transmission is enabled by switching the state of a GPIO Pin. This means that it can be used as a simple (single configuration) stand-alone transmitter with no touchscreen or computer required.

To be edited:: !!!

Keyed Transmit Mode

In keyed transmit mode, the stream is only sent when a GPIO pin is raised from 0v to 3.3v. An LED connected through a current limiting resistor (470 ohm?) is illuminated when the stream is active. By default, the key signal is input on pin 12 of the GPIO connector. This input is also known as WiringPi 1 or BCM 18. The default pin for the indication LED is pin 7 (WiringPi 7 or BCM 4). These pins are marked as 12 and 7 on the Digithin connector on the Portsdown GPIO Extender Card.

If you want to use different pins, refer to this chart https://wiki.batc.tv/PTT_and_band_switching#Summary_of_GPIO_connections to look up the WiringPi Numbers and then edit line 209 of rpidatv/scripts/startup.sh.

/home/pi/rpidatv/bin/keyedstream 1 7

The WiringPi number for the switch is first, followed by the WiringPi number for the indicator.

Once you have the hardware in place, you can set up your Portsdown to boot-up into Keyed Streaming Mode. From the console, go to the System Setup Menu, and select option 1, Autostart. Then use the arrow keys to highlight "Keyed_Stream_boot" and then (very important) press the space bar to select it. Then press enter.

You can now test the streaming from the console by selecting "Shutdown and Reboot Options". Then select Option 2, "Reboot Now". Test that the stream stops and restarts in response to the swicth and that the LED works. If you are happy with the stream, you can disconnect your PC and leave the streamer to run.