C790 is an HDMI to MIPI CSI-2 board compatible with Raspberry Pi single board computers featuring a 40-pin GPIO header that adds both HDMI input up to 1080p60 and I2S audio input to the popular Arm SBC.
The solution can be useful for IP KVM solutions as we’ve seen with the PiKVM v3 and PiCast portable KVM switch, or to capture video and audio from a camera that outputs HDMI with audio through the board’s MIPI CSI camera interface and I2S input signals on the GPIO header.
C790 specifications:
- Supported SBC’s – Raspberry Pi Zero, 3B, 3B+, 4B, CM3, CM4 with MIPI CSI-2 input port (Note: Raspberry Pi 4 is limited to 1080p50 due to 2-lane MIPI CSI-2, CM4 supports 1080p60)
- Main chip – Toshiba TC358743XBG HDMI to CSI-2 bridge chip up to 1920×1080, 60 FPS
- Video and audio input – HDMI port up to 1080p60
- Video Output – 2-lane (15-pin) or 4-lane (22-pin) MIPI CSI-2 Tx up to 1080p60
- Audio Output – 4-pin I2S connector wired to 40-pin GPIO header
- Power Supply – 3.3V DC
- Dimensions – 45 x 30 mm
- Weight – 10 grams
The seller points customers to the wiki for the BLIKVM project for instructions showing how to configure HDMI input and record video and audio with up to Raspberry Pi 4 using tools such as v4l2-ctl and GStreamer (gst-launch-1.0). The Raspberry Pi 5 is also supported, but since the Broadcom BCM2712 SoC does not come with a video encoder, the steps in the wiki are different. Note there are several versions of the board, and the C790 is the newest with improvements such as HDMI backpowering and two MIPI CSI connectors over the previous C780 and C779 boards.
I first discovered the C790 HDMI to MIPI CSI+I2S adapter on Banggood where it is sold for about $32, but you’ll also find it on Amazon and Aliexpress offers the lowest price for about $23 including shipping.
Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.
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I am curious as to legality of such device.
After all, who pays for HDMI licensing for this rather consumer-side device?
HDMI licensing fee is $0.05. Say they sell 5,000 devices – is the HDMI organization going to pursue them for $250? The bigger problem is the HDMI organization demand of a minimum $10K/yr fee to be a member. One wonders why there is still a fee on a 22 year old technology.
It doesn’t support HDCP.
Again, will lawyers hunt me for using this board in any capacity without adopter license?
I might be wrong, but I think the HDMI license is only required when using the HDMI name and/or logo (OK, HDMI is shown on the board, so that might be an issue).
We recently wrote about M5Stak CoreMP135 controller which comes with an HDMI port, but they only call it “HD video output” because of the HDMI licensing issue.
https://www.cnx-software.com/2024/04/30/m5stack-coremp135-a-linux-powered-industrial-controller-based-on-stm32mp135-cortex-a7-mpu/
Again, it would be so much better if there was an easier and all-encompassing explanation to madness in HDMI licensing scheme.
It is a racket where you send them thousands of dollars for very little in return. Send us cash and then we won’t sue you. Like MP3, H264, H265, etc. H265 backfired. The send me cash demands were so high hardly anyone is using it.
The more sensible licensing groups simply make a carve out and say first 100,000 units are free. That lets all of the tiny companies avoid the licensing mess.