Virginia Tech Ground Station TNC Interfacing Tutorial Zach Leffke, MSEE ([email protected]) Research Associate Aerospace Systems Lab Ted & Karyn Hume Center for National Security and Technology 3/23/2018 Agenda VHF/UHF • TNC Connection Overview 3.0m Dish Antennas • KISS Protocol 4.5m Dish • AX.25/HDLC Protocol • AFSK/FSK/GMSK Modulation • ….System Review…. • OSI Stack • Remote Connection Students assembling • VTGS Remote Interface 4.5m Dish • Summary Deployable Space@VT Ops Center 1.2m Dish GNU Radio at work (students preparing for 2016 RockSat Launch) 3/23/2018 TNC Interfacing Tutorial 2 Preview of the Finale…………… Primary Ground Station - UPEC Host Computer Client Software TNC TC SW TNC SW SoundCard AX.25 AX.25 KISS Interface KISS HDLC RADIO Localhost DATA FM TCP TCP AFSK D to A LOOPBACK IN RF Spacecraft IP IP IP IP MAC C&DH Audio Audio Comput HOST OS NETWORK RADIO er TC SW FIRMWARE AX.25 AX.25 KISS HDLC KISS AFSK SERIAL Remote Ground Station - VTGS FM SERIAL RF Host Computer Telecommand (TC) TTL Serial Software TNC TNC SW SoundCard AX.25 INTERNET KISS Interface HDLC RADIO DATA FM TCP AFSK D to A HOST IN RF OS IP NET VPN CONNECTION MAC Audio Audio Radio 3/23/2018 TNC Interfacing Tutorial 3 TNC Connection Overview TNC Implementation Types Hardware Radio DATA Jack Specific Interface Examples 3/23/2018 TNC Interfacing Tutorial 4 TNC Implementation Summary • Multiple implementation options exist • Hardware TNC Ground Station • Software TNC + Sound Card • Software Defined Radio Receiver • Software Defined Radio Transceiver • Hybrid SDR RX / HW Radio TX implementations 3/23/2018 TNC Interfacing Tutorial 5 Hardware Radios – Common for Satellite 3/23/2018 TNC Interfacing Tutorial 6 Hardware TNCs 3/23/2018 TNC Interfacing Tutorial 7 Radio Sound Card Interfaces • Good ones offer optical isolation (optocouplers). • Appear as a soundcard to host computer OS. • HW control of TX/RX volume. • Also used for non-packet modes. Make sure one with the proper capabilities is selected. • Different non-sound related options available (such as PTT control, and CW keying). Again, make sure one with the proper features is selected. 3/23/2018 TNC Interfacing Tutorial 8 Software Defined Radios Receive Only Transceivers (TX & RX) B-Series Mini Red USRP Pitaya LimeSDR SideKiq Blade E-Series RF USRP SDRPlay B-Series USRP N-Series USRP X-Series USRP See for more: https://www.rtl-sdr.com/roundup-software-defined-radios/ 3/23/2018 TNC Interfacing Tutorial 9 The ‘S’ in SDR?...here are a few… SDR# GNU Radio HDSDR gqrx GNU Radio gr-fosphor (GNU Radio) 3/23/2018 TNC Interfacing Tutorial 10 Putting it all together LOTS of options exist…….. ….and combinations of options… ….how to decide?!?!?!….. ….Lets go over some fundamentals…….. 3/23/2018 TNC Interfacing Tutorial 11 Hardware TNC Ground Station Serial Audio/NRZ AX.25/KISS PTT Host Computer HW TNC HW Radio Antennas Host Computer Hardware TNC Hardware Radio VHF RF VHF RF Chain Client COM RADIO SERIAL SERIAL Audio/NRZ/DIO DATA Software PORT PORT UHF RF UHF RF Chain 3/23/2018 TNC Interfacing Tutorial 12 Software TNC + Sound Card Ground Station USB / Serial Audio/NRZ ‘audio’ samples PTT Host Computer SoundCard HW Radio Antennas Interface Host Computer Hardware Radio Sound Card Interface VHF RF Sound VHF RF Chain Card Sound SPKR TX DATA Driver Card IC Client TCP/IP Software USB (ADC/DAC) MIC RX UHF RF UHF RF Chain USB AX.25/KISS HUB Software TNC FTDI COM Port USB DTR PTT PTT PORT IC (PTT) 3/23/2018 TNC Interfacing Tutorial 13 Software Defined Radio Receiver USB Digitized RF Samples (IQ) Host Computer Antennas Software Radio Dongle Host Computer Software Radio Receiver I IF RF LO SDR D A Client TCP/IP Software Audio IQ SDR 0° 1 Signal USB IF RF RX RF RF Chain RF AX.25/KISS Samples Driver 90° 2 LO Software TNC D A USB PHY USB Processing Port USB LO Q IF RF 3/23/2018 TNC Interfacing Tutorial 14 Software Defined Radio Transceiver N-Series USRP Ethernet (UDP/VITA-49) Digitized RF Samples (IQ) Host Computer SDR Transceiver Antennas Software Radio Transceiver I IF RF LO Host Computer D A 0° 1 IF RF RX 90° 2 LO D A RF RX VHF RF Software Radio LO Client TCP/IP SDR Q IF RF Signal Processing IQ Ethernet Software AX.25/KISS Driver RF (Link and Physical Layer) Ethernet I IF RF CHAIN LO Ethernet PHY Ethernet D A RF TX UHF RF 0° 1 LO IF RF TX 90° 2 D A LO Q IF RF NOTE: This is basically the chosen VTGS architecture 3/23/2018 TNC Interfacing Tutorial 15 TNC Connection Overview TNC Implementation Types Hardware Radio DATA Jack Specific Interface Examples 3/23/2018 TNC Interfacing Tutorial 16 Hardware Radio DATA Jack ICOM-9100 Example What is it for? • Used for packet operations. • Bypasses audio filtering (which can distort digital communications). • Standardized PS-2 Connector and pinouts across vendors. • High speed (9600 baud) and low speed (1200 baud) packet access. • Connects to ‘Radio Port’ on TNC. 3/23/2018 TNC Interfacing Tutorial 17 FM Transceiver (simplified) Tuning Control (the BIG knob) Demodulator Volume RX Channel AGC (FM Discriminator) Control Filter De-Emphasis Speaker RF IF LO Pos(+ ) RX 1 Audio C FM 2 TX Filtering ALC Modulator Microphone LO RF IF IF AUD TX/RX LO Control TX Filter TX PWR Pre-Emphasis Control RF Stage IF Stage Audio Stage 3/23/2018 TNC Interfacing Tutorial 18 FM Transceiver – DATA Jack Tap Points 6 4 5 RF IF LO Pos(+ ) RX 1 C 2 1b* 1a* 2 TX LO 3 RF IF IF AUD LO *NOTE: • Selecting 1200 Baud packet mode on radio menu connects 1a tap point • Selecting 9600 Baud packet mode on radio menu connects 1b tap point • Unsure if pins 4 and 5 are affected by this menu selection. (TEST!) 3/23/2018 TNC Interfacing Tutorial 19 Hardware Radio DATA Jack From IC-9100 Manual Probably want MAIN assigned to uplink so that when PTT is triggered, the radio transmits on the Uplink Frequency. SUB would then be assigned to Downlink noting the comments below. Could be totally wrong about this, especially if IC-9100 has a ‘satellite mode’ of operation that overrides these settings. 3/23/2018 TNC Interfacing Tutorial 20 Hardware Radio DATA Jack DATA Jack to TNC Pinout/Cabling TNC or Soundcard Notes TNC or Soundcard • Each vendor is different. DATA Jack Signal Interface Equivalent • Different connector styles, different Signal pinouts, different settings. • Must consult the manufacturer documentation to properly configure and fabricate interface cable. • Some TNC/Soundcard vendors sell pre- fabricated radio specific interface cables. • MUST pay attention to signal levels (volume control) on DATA IN (1), DATA OUT (4), and AF OUT (5) pins to avoid signal distortion (lost packets). 3/23/2018 TNC Interfacing Tutorial 21 Hardware Radio DATA Jack – Additional Notes Volume Control Squelch Pin (6) • The AF OUT (5) and DATA OUT (4) Pins bypass • SQL (6) connection is optional. Purpose is to inhibit Transmit when open (signal detected). the majority of the audio conditioning For satellite work, recommend leaving circuitry. This is to avoid distortion. This disconnected so that the squelch can be means that the VOLUME control knob on the completely opened on the radio. This will radio has no effect on the voltages output on allow a human operator to listen to signals too weak to decode (like near AOS/LOS) to these pins. The human operator can set the monitor system performance without volume of the radio speaker to a comfortable inhibiting transmit (uplink) capability. level for monitoring without affecting the • This pin is most useful for Terrestrial APRS use voltages output on these pins. Most TNCs when in a cluttered RF environment (many have a configurable ‘input gain control’ (or transmitters on same frequency and bursty). This pin is usually connected to a ‘Data Carrier similar) setting to set this at an optimal input Detect’ Pin on the TNC to inhibit TX when level for the TNC. Most sound card interfaces signals are detected on the channel in order have an ‘RX knob’ which is essentially a to avoid packet collisions. volume control for the same purpose. 3/23/2018 TNC Interfacing Tutorial 22 Hardware Radio DATA Jack – Additional Notes Push To Talk (PTT) • The PTT (3) pin is used to enable transmit on the radio. • It is tempting to connect directly to the TNC (that’s what the manual says to do right!?!?). • For satellite work, usually this is not actually desirable because there are multiple devices that need to ‘see’ the PTT signal to switch the entire system (not just the radio) into a transmit state. • Devices that need to see the PTT pin include the Low Noise Amplifiers, The High Power Amplifiers, the Radio and sometimes additional devices (such as coax relays) depending on the specifics of the ground station design. • Normally, this pin out of the TNC is used to trigger a device called a ‘sequencer’ that has multiple PTT output channels with configurable delays between each channel. The radio PTT signal on the DATA jack is usually the LAST PTT signal to be enabled. • More on Sequencing later……..its important! 3/23/2018 TNC Interfacing Tutorial 23 TNC Connection Overview TNC Implementation Types Hardware Radio DATA Jack Specific Interface Examples 3/23/2018 TNC Interfacing Tutorial 24 Some Examples • Hardware TNC And Radio: KPC-9612+ TNC & ICOM-9100 • Sound Card Interface and ICOM-9100 • Software TNC Examples (for sound card interfaces) • Software Radio Receiver Example • ‘Client Software’ Examples 3/23/2018 TNC Interfacing Tutorial 25 HW TNC To HW Radio Example KPC-9612+ ICOM-9100 FRONT REAR • Port 1 – Low Speed (AFSK1200) • Port 2 – High Speed (FSK9600) • Computer = Serial 3/23/2018 TNC Interfacing Tutorial 26 HW TNC To HW Radio Example Cable Fabrication Time! 3/23/2018 TNC Interfacing Tutorial 27 KPC-9612+ TNC to ICOM-9100 DATA Cable XCD PTTP TXA AF OUT (1200bps) Port 1 ICOM-9100 1 6 2 GND SQL 7 SQL 3 8 LOW SPEED DATA CABLE DATA OUT 4 (9600bps) 9 5 SHIELD DATA2 SHIELD DB-9 Male GND (PS-2 Male) KPC-9612+ RXA DATA IN PTT SHIELD RXA SHIELD Port 2 HIGH SPEED DATA CABLE 1 GND 9 2 10 3 GND ---- ---- 11 Oscilloscope ---- ---- ---- ---- 4 GND CALIBRATION CABLE ---- ---- 12 RXC ---- 5 ---- Eye Diagram 13 (OPTIONAL) XCD 1 2 3 4 6 Monitor 14 1 2 3 4 7 On/Off 15 8 GND SHIELD RXC DB-15 Male RXA (NOT HD version!) RX S/N OFF ~ A V V mV 123 ~ Handheld DMM Handheld mA NOTES μ RXA GND A RX SNR / §Ù .