Portsdown 5 Introduction

Introduction

The Portsdown 5 is a Digital ATV Transmitter, receiver and test apparatus designed to run on a Raspberry Pi 5 with a Raspberry Pi 7 inch Touchscreen Version 1. The newer, higher definition, Touchscreen 2 is not yet supported, although provision is being made for possible future support.

Some of the Portsdown 5 software (the receiver and the test equipment) will run on a Raspberry Pi 4, but the H264 encoding used for transmit requires the upgraded processor in the Raspberry Pi 5.

There are 3 target hardware configurations for the Portsdown 5:

• Raspberry Pi Foundation 7 inch touchscreen Version 1 (800x480) or compatible DSI screen
• HDMI display (480, 720 or 1080) with a mouse.
• Web control (with or without touchscreen or HDMI display)

Web control is available alongside either of the other configurations, but the HDMI display (with mouse) and touchscreen are mutually exclusive.

The functionality of the Portsdown 4 is slowly being ported to the Portsdown 5, but there are limitations because it is not possible to access the hardware H264 video encoder used in the Portsdown 4 from the 64-bit operating system of the Portsdown 5. At the current stage of development, new builders are still recommended to build the Portsdown 4.

Construction

When considering the mechanical design, the normal (Raspberry Pi 7 inch version 1) touchscreen display should be mounted with the PCB legend the right way up. This compromises the viewing angle, but is required for VLC which cannot flip its output. The software does have the ability to drive the display in either orientation for most modes, but video in VLC will appear inverted if the wrong direction is chosen.

In due course, the software might support the Touchscreen 2 in the normal (landscape) orientation (with the PCB legend the right way up) as it has a better viewing angle.

When connecting the Touchscreen, it should be connected to the port labelled "CAM/DISP 0" with the conductive side of the ribbon facing the network port. On the display, the conductive side of the ribbon should be "upward" (visible) in the connector.

Future connections of the Touchscreen 2 should be made to the connector labelled "CAM/DISP 1"

The draft GPIO connections for the Portsdown 5 (which have changed significantly from the Portsdown 4) are here Portsdown 5 GPIO Connections

Compatible Touchscreen Displays

The Portsdown 5 has been designed to be compatible with any DSI-connected 800x480 touchscreen. It is not compatible with HDMI touchscreens or DPI-connected displays. It is not possible to guarantee compatibility with any particular touchscreen (apart from the official Raspberry Pi screen), but the Waveshare 7 inch display pictured below seems to work well as long as it is powered through the power connector; the pogo pins have proved unreliable.

Current Implemented Functionality

Capabilities are slowly being added to the Portsdown 5. The following functionality is working:

• DATV Receive using a PicoTuner or MiniTiouner
• Stream Viewer
• LimeSDR BandViewer
• RSPdx (and RSPdx-R2) BandViewer

The following functionality is working but has some known bugs:

• LimeSDR Noise Figure Meter
• LimeSDR Noise Meter
• Signal Generator for LimeSDR and DATV Express
• Frequency Sweeper
• DMM Display
• AD8318 Power Display

The following functionality is not yet implemented:

• DATV Transmit
• Sending Streams
• Pluto-based test equipment
• Airspy BandViewer
• RTL-SDR BandViewer and receiver
• DATV Tools
• Locator Calculator