MISRC - Multi Input Simultaneous Raw RF Capture

Hardware - Firmware - Software - Usage example

V1.5 with Tang Nano 20k on the FX3 to Tang Nano 20k adaptor PCB.

Description

MISRC is a device to capture two signals at 12-bit and up to 40 MSPS (20 Mhz bandwith) (This could be extended to 80 MSPS in the future) and an additional 8-bit's (2-bit's for v2.5) of binary (auxiliary data) over USB 3.0.

It is intended to capture modulated tape deck RF for software demodulation, but also baseband CVBS/S-Video (Composite) video signals for software decoding, and can be used as a direct stream Oscilloscope but limited to 2vpp input voltage.

The Decode Projects:

• VHS-Decode
• HiFi-Decode
• CVBS-Decode

Provide decoding for a wide range of videotape formats, HiFi audio and even RAW or Baseband composite decoding with free and powerful software time base correction with full post filtering control over the signal processing.

Possible capture examples:

• Capture 2x CVBS
• Capture 1x S-Video (Y & C)
• Capture Video RF and HiFi RF simultaneously
• Capture Video RF and CVBS simultaneously
• Capture 4ch of 24-bit 48khz audio with AUX pins via integrated or external clock-locked ADCs

Note

It may be useful for other purposes as well, as it is built as a generic ADC with configurable filtering.

Hardware features

• Dual ADC / Dual Input (BNC Connectors)
• 6 Extra Aux inputs for audio ADC modules etc
• Two 12-bit 40msps ADCs: AD9235
• Selectable input gain (8 steps) (using AD8138 op-amp)
• Selectable ADC range (1V or 2V)
• Selectable input impedance (75, 50, 37.5 and 30 ohms)
• DC or AC (pre- or post-termination) coupling
• Zero-adjust to compensate DC offset
• Latching clipping indicator (automatic resetting on v2.5)
• Clock source selectable: USB PLL (FX3 setup), crystal or external
• Clock output SMA for external devices (In/Out for V2.5)
• Melted PCB Traces

Costs

Tip

You can support the development and production of the MISRC platform here.

• PCB: 20-30USD
• Parts 100-150USD
• Single unit total production cost is currently 260-300USD.
• Order a V1.5 Development MISRC

Note

These are off-shelf PCBs and USB 3.0 devices that you add to the MISRC PCB.

• Tang Nano 20k - buffer / data output over HDMI.
• MS2130 - Order Link 1 / Order Link 2 - HDMI raw data stream capture.

Tip

You can order pre-made adaptor PCBs here for V1.5 boards with the headders for the FX3.

Firmware (Tang Nano 20k)

To be able to use the Tang Nano 20k to send data over HDMI, it needs to be flashed once via USB connection:

Software

Supported operating systems with direct links to the latest release (also available on the releases tab):

Note

The arm64 builds for Windows are untested and considered experimental!

The packages contain two command-line applications, misrc_capture and misrc_extract. For detailed usage information see the misrc_tools readme and the usage example down below.

If you want to build the tools yourself, see the instructions in the misrc_tools readme.

Interface 0 - USB Video
Interface 4 - HIDDevice

Capture / Usage example

Tip

Pre-built Binaries is available on the releases tab.

misrc_capture is a simple command line interface program to capture from MISRC boards using hsdaoh to which leverages data capture over HDMI with MS2130 "U3" cheep HDMI capture cards that have YUV support and full-frame signal acesses.

Create a folder which you wish to capture inside, open it inside terminal and then run misrc_capture.

Example with FLAC compression:

misrc_capture -p -f -l 8 -a video_rf.flac -b hifi_rf.flac 

Example RAW:

misrc_capture -a video_rf.s16 -b hifi_rf.s16

Example with AUX pins capture (PCM1802 audio example)

misrc_capture -p -f -l 8 -a video_rf.flac -b hifi_rf.flac -x pcm1802.bin

You can also define its directory path of each RF stream manually:

misrc_capture -p -f -l 8 -a /mnt/my_video_storrage/video_rf.flac -b ../../this/is/a/relative/path/hifi_rf.flac

Press Ctrl+C to copy and Ctrl+P to past your config from a notepad or txt file.

Use <+> to move edit position on the command line to edit the name or command while in terminal and Enter to run the command.

Ctrl+C Will kill the current process, use this to stop the capture manually.

misrc_capture -p -f -l 8 -a video_rf.flac -b hifi_rf.flac -x baseband_audio.bin

Setting Up the MISRC

• Connect your 5V USB-C to the Tang Nano for power.

• Connect your HDMI cable (copper or fibre) to your Tang Nano for data output to the MS2130 or MS2131.

• Connect the desired sources to the BNC inputs and select suitable impedance and AC or DC coupling.

Note

You will want to use 2vpp range rather than 1vpp range to make use of the 12-bits range.

Install OCENAudio or alternatives like Audacity it will see captures as a 40khz 16-bit file.

Run a 3-second test capture in FLAC, to be automatically reloaded for viewing.

misrc_capture -p -f -B -t 3 -a test.flac

Start the capturing process for setting the DC offset then gain:

- Reset clipping LEDs (always on after start or major adjustment) 
- Increase gain during capture until clipping LED lights up
- Decrease gain one step and reset clipping LED
- Repeat for the second channel if in use.

• Stop capture and verify levels are acceptable in your audio DAW and the signal is centred.

Once happy, then do a full test capture to verify.

Caution

• NEVER use USB for any other heavy-load task (like external HDD/SSD drives, USB network adaptors, YUV capture devices) during capture.
• Do not connect/disconnect any other USB device during capture, a dedicated USB 3.0 to 3.2 Gen 2 card is ideal for dedicated capture stations as it ensures dedicated bandwidth/power if you have other items that require USB.

Design

MISRC is loosely based on the Domesday Duplicator (DdD) a LaserDisc focused (ld-decode) FM RF Archival device.

It is built around the AD9235 analogue to digital converter by Analog Devices and is heavily based on the evaluation board circuit given in its datasheet with the AD8138 Op-Amp providing adjustable fixed gain.

The MISRC like the DdD it originally used the Cypress FX3 SuperSpeed Explorer board for a USB 3.0 data connection, and using Sigronk for capture, with hopes to not use the DE0 FPGA, this ended with the adoption of the Tang Nano 20k and MS2130 "data over YUV" method being used.

License

The hardware, firmware and software is released under different open-source licenses. You can read the License here