Hi @berger (and anyone else who’s interested, of course) ,
Here’s a brief tutorial showing how I made up the active cable that allows my unmodified Raspberry Pi HQ camera to work with the Jetson Nano.
Overview
Here’s a diagram of what we’re trying to make. The cable passes through all the signals from the Jetson Nano to the camera unmodified, apart from the ENABLE signal on pin 11. This is passed through the SN74LV1T34 buffer to shift the logic levels from the 1.8V that the Nano uses to the 3.3V that the camera needs.
Power for the buffer IC is taken from the 3.3V and GND lines, and is decoupled using a 100nF multilayer ceramic capacitor (as the IC is a long way from any other decoupling capacitors and you can get weird oscillations and other unwanted effects if you don’t decouple your power supplies properly).
Parts List
Here’s the list of parts I used (not including the camera and cable it was supplied with). I’ve included the order codes for Farnell, which is where I got the parts from, though there’s nothing exotic here so you should be able to source the parts from your favourite supplier.
You’ll need one of each of the following:
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FFC/FPC Cable, 15 core, 1mm, SAME SIDED CONTACTS 200mm (3385342)
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SN74LV1T34DBVR BUFFER GATE, LEVEL SHIFTER, SOT-23-5 (3119564)
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IC Adapter, SMD Connector, SC/SOT/TSOT/TSOP to 6-SIP (1654365)
-
100nF Multilayer Ceramic Decoupling Capacitor (2309020)
(I grabbed the last one out of my bits box, so the Farnell order code is probably different. However, this is not a critical part, so any similar decoupling capacitor would do and you might be able to get away with omitting it completely).
Here’s what they look like…
About the Cable
It is important to note that the second cable has the connectors on the SAME side, which is different to the cable originally supplied with the camera. This is because the second cable will be soldered on to the end of the first and therefore act as an extension. Using another cable with contacts on the opposite side would reverse the connections between the camera and the Jetson, likely shorting 3.3V to GND and doing other bad things. Don’t do that.
Step 1
Carefully remove pins 1, 2 and 5 from the IC adapter board (as we don’t need them and they’ll get in the way). Make sure not to lift the pad off the board for pin 2 as we’ll need to solder a wire on to that later. Solder the IC onto the board, making sure it is oriented correctly (pin 1 in the top left when viewed like this).
Step 2
Solder on the decoupling capacitor.
Step 3
Carefully cut either side of 11th core at the end of the new (same side contacts) cable and bend it upwards. This’ll let us connect a wire to that core later on.
Step 4
The pin spacing on the IC adapter is close to what’s needed to solder it directly to the cable, but a bit of adjustment is needed first. You need to space the three pins out so that there is 4mm between each adjacent pair (i.e. 4mm between pins 3 & 4, and 4mm between pins 4 & 6).
When you lay the IC adapter on top of the exposed cable contacts, ping 3, 4 and 6 on the adapter should line up with cores 7, 11 and 15 in the cable.
Step 5
Solder the adapter to the original cable that came with the camera, then solder the new cable on to the end. You should have something that looks like this (though hopefully a bit neater!).
Step 6
Solder a short piece of wire between the bent core 11 on the left hand cable to pin 2 on the IC adapter board.
Step 7
Mark the cable so you know which way round it goes (e.g. J for Jetson and C for Camera).
Step 8
Test for shorts between adjacent lines and open circuits using a multimeter. Rework as required before testing with the real Jetson Nano and camera.
And Finally…
If you’re happy that it works, then some sort of mechanical protection around the area you operated on is probably a good idea.
Since the SN74LV1T34 buffer can operate with 3.3V inputs when powered from a 3.3V supply, you can use the cable with a Raspberry Pi as well as with the Jetson Nano, so if you move the camera between devices (as I do), you don’t have to keep swapping the cable.
Good luck!
Simon