Hi, in a prototype instrument I have panel-mounted a Raspberry Pi 7" Touchscreen, and I’ve also mounted a Raspberry Pi Compute Module 4 IO Board on the rear of the touchscreen. This setup gives me a Pi 4 with built-in RTC, in a shallower space than the standard Pi 4 with a stacked RTC board behind it. This geometry which works well for my instrument’s case design.
However I’ve just discovered that the Compute Module 4 IO Board has 22-pin DSI Video connectors of about 0.5mm pitch between pins, which are physically incompatible with the Pi 7" Touchscreen’s 15-pin DSI connector which has about 1mm pitch between pins.
There are also adapter boards such as this one - though they require two different cables as well, i.e. one cable of each type 15- and 22-pin - less elegant than a simple adapter cable, but it’s another method:
I was wondering if Core Electronics sells a suitable 22-to-15 pin adapter cable or adapter board…
I then noticed this cable CEO4763 sold as a “Raspberry Pi Zero Camera Adapter” which looks like a possible solution to my problem - if the Pi Zero’s video connector is the same 22-pin arrangement that the CM4 IO Board uses:
Could you please clarify if the above Pi Zero Camera Adapter cable is the correct solution for my Pi CM4 IO Board (22 pin) to Pi 7" Touchscreen (15 pin) video cable problem? If not, is there another solution?
I took a look around, and it seems that the CM4 uses the same connector as a Zero, but with all 4 MIPI lanes connected to the processor, rather than 2 on every other Pi. This means that with custom drivers you could get it working faster, but for your use case, I believe you can just use the adapter cable you linked. More info here:
I linked to Waveshare’s site for this adapter in my first post above.
Further, I’ve just found that Amazon sells the relevant Waveshare adapter board:
Of course, it needs both a 22-pin and a 15-pin DSI / CSI video cable to work.
Given this incompatiblity which we were both unaware of, you may wish to consider selling a kit which contains (1) the Waveshare CM-DSI-ADAPTER board, (2) a 22-pin DSI cable, and (3) a 15-pin DSI cable? Plus instructions on which way up the cable goes at the CM4 end - which seems tricky to clarify?
It seems unfortunate that Raspberry Pi has created this incompatibility issue, however the above looks like a solution - subject to reading the " 7" Raspberry PI display and compute module 4 " forum thread which I linked earlier in this post.
Some good news that simplifies this issue somewhat -
Looking again at the Waveshare website, I realised that their CM-DSI-ADAPTER actually includes the required 22-pin DSI cable.
I can confirm this is the case as, having received one of them from Amazon yesterday, it does include a short 22-pin DSI cable, around 10cm long.
Thus if you wish to assist future purchasers of the Pi Compute Module 4 IO Board to solve this DSI video incompatibility issue, they would only need:
The Waveshare CM-DSI-ADAPTER Adapter Board (which includes a short 22-pin DSI cable), plus
a 15-pin DSI cable. On the 15-pin end of it, a 10cm-long cable comes with the Pi 7" Touchscreen; or if needed, Core Electronics already sells 15-pin DSI cables as “Flex Cable for Raspberry Pi Camera” in several lengths such as 20cm or longer.
Thus instead of considering the 3-part kit which I described above, you could consider selling the Waveshare CM-DSI-ADAPTER adapter, with a note in its description referring customers to also buy one of your 15-pin “Flex Cables for Raspberry Pi Cameras” of whichever length they need, if the 10cm cable that came with their Pi 7" touchscreen isn’t long enough.
I hope that this information simplifies this question for your catalog staff, and for your customers who read through this thread in the future.
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