A Universal Mobile / Embedded SSTV System

Purpose
Disclaimer
Features
Schematics
PCB
Download
Usage
Notes & comments
in the Press
Credits

Purpose

The (nearly) finished SSTV System

An example picture sent by this SSTV system

Based on the Universal PIC Board and the SSTV Test Generator this page presents a mobile SSTV System, usable for mobile SSTV by operators as well as automatic SSTV system used in bacons or other unmaned mobile SSTV applications like for example balloons.

DISCLAIMER THIS SITE INCLUDING ALL ITS CONTENT (TEXT, PICTURES, BINARIES ETC.) IS NOT ALLOWED TO BE USED IN CRIMINAL OR ILLEGAL ACTIVITIES. IT IS FOR NON COMERCIAL PURPOSE ONLY! I AM IN NO WAY RESPONSIBLE FOR ANY EXTERNAL CONTENT POINTED TO FROM THIS SITE. UNDER NO CIRCUMSTANCES I AM RESPONSIBLE FOR ANY DAMAGES TO YOUR RADIO, PC OR OTHER EQUIPMENT. USE THIS SITE AND ALL OF ITS CONTENT AT YOUR OWN RISK! BY USING THIS SITE AND ITS CONTENT YOU HAVE ACCEPTED THIS DISCLAIMER.

Features

Every OM beeing mobile QRV may know the situation where you would like to describe your QSO partner, maybe some hundred kilometers away, some situaton or picture. As we know - a picture says more than 1000 words. For "normal" mobile operators using multimedia mobile phones this is normaly not a big problem but for HAM's it is not that easy. Sure we have more possibilities sending still images by using high quality cameras, laptops and good software - but we will pay the price in size and weight. I bet most of us wont carry a mobile transceiver, power source / batteries, amplifier, laptop, camera and cables etc. with us. So thats why I designed this mobile SSTV system in size of just a third of a Euro Board which connects to your transceivers NF input.

In the past there where already some devices with resonable size like the Kenwood VC-H1 which allows to be mobile SSTV QRV. But unfortunately they disapear from the market but maybe still available on eBay.

The Kenwood VC-H1

Despite of the fact that the presented SSTV system is very simplistic (just 3 buttons and 2 LED's) it has a lot to offer:

It transfers pictures in Martin1 mode either as color or B/W with 320 x 240 or 320 x 256 pixels

Supports SSTV VIS code

Free text station id transmission after SSTV picture transmission in CW (can be turned off)

Send a captured picture many times using either color or S/W

Supports two user defined action buttons

3 LED's for status display (Power, On Air, Error)
Built in battery backed real time clock (RTC) for date and time display in pictures or CW transmissions

Temperature sensor to transmit the current temperature either as text inside the picture or as CW

User definable statustext for display in transmited pictures

Statustext position in picture can be top, middle, bottom or off

Free fore- and background color selection for the statusbar

By using a Font Editor (see here) user defined character sets can be created and uploaded to the SSTV system. This way users can create small graphics, icons or even foreign language fonts (eg. cyrillic) for use in the statustext

For diagnostic purposes a colorbar pattern test image can be transmitted with or without statustext

It's possible to send camera pictures mirrored

Configuration is done via a RS232 connected PC and a simple terminal software like Windows HyperTerm

In depth diagnostics like modifying camera registers or dump the EEPROM conten can also be done using the PC

A analog FBAS B/W video signal for calibration is available on connector J3

Possibility to control a receivers PTT via Pin 3 of J1, J2 ord J4

Very small form factor. The whole system consists of two stacked boards each 10 cm x 5,3 cm in size

Can be very easily integrated into other projects

Pin 2 of connector J1 and J2 can be used as PTT controll. It is high during a transmission and low otherwise

Due to the small form factor a dual sided board was necessarry however the usage of SMT parts could be reduced to only a few. The SSTV Board is connected to the CPU board vie connector BUS so that both boards build a stack.

Schematics

A description of the CPU board con be found here. The digital camera module CAM-3188A which uses a OV7620 CCD Sensor is controlled by using a I2C bus the same way as the Temperature Sensor TC74 and the real time clock DS1307 are. To ensure that picture are taken in good quality most of the time the camera module is run in automatic mode for white balance, brigthness etc. If a picture should be sent the camera writes it into memory IC4 as a YUV byte stream. From there the CPU reads the data calculates RGB from YUV and then converts RGB into NF frequencies for sending. 1900 Hz represents black, 2300 white and 1500 Hz represents a sync pulse. This NF signal is processed by one ore two NF filters before it is sent. By opening and closing the solder jumpers Bx1 - Bx3 the filters can be configured. This way you can omit the switched capacitor filter IC3 a MAX7419 which is a litle bit tricky to solder and use only the following R/C filter. The image memory uses a 3V power supply and therefor IC6 is used to provide this.

Download

You can download zip files including a pdf file of the PCB and schematic as well as the boot loader and the firmware. First burn the bootloader to the pic microcontroller an then use the bootloader to burn the firmware. Optionally you can burn the firmware direct without using a bootloader.

Version	File
Version 1.0	sstv-v1.0.zip
Version 1.5	sstv-v1.5.zip
Version 1.10	sstv-v1.10.zip

The PCB

These are some pictures of the v1.0 board. Newer board layouts meight be released so please have a look at the zip files in the download section.

Componen placement PCB full view

PCB top side PCB bottom side

Usage

To be SSTV QRV the system must be first configured. After connecting it to a PC's serial port using a 1:1 RJ-45 to DB9 cable and setting the communication parameters in your favourite terminal software (e.g. HyperTerm) to 9600 baud, 8 data bits, 1 stop bit, no parity and hardware handshake the system can be powered up. You should see the main screen and the prompt > waiting for input. The input prompt is also shown after a CR/LF (press Enter key)

Following you will see the three menues/screenshots of the firmware which allows configuration, diagnostics and operation. After pressing Cc (uppercase and lowercase c you will be presented with the configuration dialog. First you should set your callsign and other station rfelevant parameters. Next connect the output on connector xxx to your PC's soundcard input and start your favourite SSTV software (e.g MMSSTV). After pressing p (lowercase p) your software should start picture reception and after a while you should see the transmitted picture. If this test was successfull you can connect the output to your transceiver and start some SSTV QSO's.

Version: 001.010 *** Main Menu *** t - Send a colorbar testpattern p - Take color picture and send it P - Take black and white picture and send it a - Start automatic mode, end with ESC A - Same as 'a' but with 'g' (10 seconds) during wait l - Resend last picture in color L - Resend last picture as BW i - Send the Station ID (OE1RIB) in CW 1 - Send the picture statusbar in CW 2 - Send the testpattern statusbar in CW c - Send interactive CW C - Configure system g - Wait 30 sec for GPS NMEA position D - Diagnostics ? - This helpscreen >

*** Config Menu *** c - Configure system c - Set clock s - Show system status r - Reset system to defaults f - Upload font a - About ? - This helpscreen < - Back to Main Menu >

*** Config Dialog *** Current time: 23.07.2010 21:30:11, Temperature: 033 C StationID: OE1RIB Send StationID after transmission (Y/N): Y Mirror camera image (Y/N): N Large (256 = Y) or small (240 = N) image: Y Key action: p Time (seconds) between pictures: 010 Macros: %C-Call, %V-Ver, %T-Temp, %d-Date, %t-Time, %L-Lat, %l-Lon %D-Day, %M-Mon, %Y-Year, %h-Hour, %m-Min, %s-Sec, %p-Pic# --- Camera Picture --- Statusbar (N-none, T-top, M-middle, B-bottom): T Current Statusbar font size (1-3) : 1 Statusbar format: %C %h:%m %L, %l, %p Current Statusbar color (RRGGBB): foreground: FEFEFE background: 0051D7 --- Test Picture --- Statusbar (N-none, T-top, M-middle, B-bottom): M Current Statusbar font size (1-3) : 1 Statusbar format: *** SSTV Bacon %C *** Current Statusbar color (RRGGBB): foreground: FFFFFF background: 000000 >

*** Diagnostics Menu *** --- OV7620 Diagnostics --- c - Reset Camera C - Take picture D - Show registers P - Dump out picture --- NF Diagnostics --- 0 - Turn tone oscillator off 1 - Turn tone oscillator on k - Sends a 1000Hz test tone 2 - send 1500Hz 3 - send 2300Hz f - Enter Frequency Word (00:00-FF:FF) F - Enter Frequency Value (00-FF) --- System Diagnostics --- r - Reset RTC and start oscillator d - EEPROM Editor i - Scan I2C Bus ? - This helpscreen < - Back to Main Menu >

Notes & Comments

The firmware of the system is written entirely in about 20000 lines of assembler code and uses about the half of the used PIC 18F458. There there is enough room for improvement like:

Development of another PCB which contains a color LCD and a microphone which connects on the bottom side of the CPU board. This way a Videomicrophone could be reated.

CAT controlling of a transceiver via the RS232 port for automatic transmission of pictures on different frequencies

Designing a way to dump a camera picture via RS232 and/or USB so we get a simple WebCam

2007-08-13 Component sources
- The Camera Module can be obtained from Sander Electronics
  http://www.sander-electronic.de/gm00031.html
- A source for the AL422B Video RAM is Zwinz Consulting
  http://www.techconsultzwinz.de/averlogic/averlogic-al422b.htm
2009-09-01 PCB Boards
A few boards are available for building the SSTV system. Contact me for details.
2009-10-07 Board and Firmware update Version 1.5
A new, slightly modified board layout with a modified 3V regulator and a better circuit for loading the RTC battery is available. There where also some modifications on the firmware. The new version provides the follwoing features:
- Send continous color pictures every 0 - 999 seconds.
- Scan I2C bus for available devices (debug feature)
- Now includes a boot loader to allow firmware updates via the serial port.
  First flash "TinyBoot18F458.hex" with your favourite PIC programmer. After this use "FlashTool.exe" to flash "SSTV-Modem.hex" to the microcontroller. Ensure that "FlashTool.exe" is configured correct eg. port parameters and "Codes to send first".
2010-05-04 Power consumption
The power consumption of the whole system (CPU board and SSTV board) is 90mA in idle mode and about 100mA while transmiting a picture.
2010-07-14 Connecting a GPS receiver
The existing firmware allows to include additional data in transmitted pictures like date/time, callsign or the current temperature. Including the current position or synchronizing the clock from a GPS receiver would be beneficial. As there is only one serial port available in the sstv system this port has either to be shared or a second, software emulated serial port has to be created to connect both, a controlling system/console and a GPS receiver. As program memory is limited the decision was made to multiplex the existing hardware serial port by using a control signal on PORT B,2. receiver.
The following picture shows how this was done.

click for larger view
The GPS receiver must use the same serial parameters as the sstv system: 9600,N,8,1. The firmware looks for NMEA $GPGGA records and if it finds a valid one it syncs the internal RTC to the GPS time and extracts latitude and longitude infoamtion. These information can later be used in transmitted pictures using the %l and %L macros.
The "g" command switches to the GPS receiver and waits 30 seconds for valid date. If it receives valid data the command finishes. If you press/send ESC during this 30 seconds the wait is canceled.
There is also a new auto mode command "A" which automatically transmits color pictures with a configurable wait time between sends (same as the "a" command"). During this wait time the serial port is switched to the GPS receiver for another (additional) 10 seconds to receive valid location data. Other than with the "g" command this 10 seconds are fixed even if valid data is received before. This 10 seconds are ADDITIONAL to the configured wait time between sends.
Latitude and longitude information can be displayed in a pictures status bar by using the %L and %l macros. The macro "%p" is also new and inserts the current picture number (only usefull in automatic transmit mode otherwise the current picture number is 0).

in the Press

This paper can also be found in the german HAM Radio Magazine
"Funkamateur" at www.funkamateur.de, Issue 08 / 2007, Page 868,
Title: "SSTV-Sendemodul auf Basis eines universellen PIC-Boards"

Credits

If you have any comments or sugestions just drop me a line.

73, OE1RIB

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