Hi, I am building the mini version of Chordata and have some questions on my hub.

My RPis don't recognize my hub.
Powering up just fine. Both 5v and 3.3v red LED lit up. No light on RGB LED though.

What I did:
I tried different RPis, zero w and RPi 4 but the same results.
Change the wires. No luck.
RGB LED doesn't lit up so I removed it but it didn't affect any.
I accidentally switched SDA and SLK wires then it recognized hub but kept printing setup error messages.
Soldering job looks good to me. I retouched the pads on U5 with soldering iron tip to make sure but the same error message.

The voltage reads are:
for SDA 3.3v, SLK 210mv. Are these in the normal range?

I am ordering more components to build spare hubs(I should've ordered 23 sets. My bad..) but I really want to find out what is the problem with my hub.

Ok, While I was reading other threads, I found out that the RGB LED is still not implemented on software.

Hi!
I have no experience with the miniHub, but if you are sure the jumper cables are ok then it's probably a soldering issue.
Perhaps @valor, creator of the miniHub can give you more specific advice.

In order to confirm the RPi can see your Hub try running this command:

i2cdetect -y 1

You should get a positive in the 0x73

    How long are your wires and which pins are you connecting to on the RPi?
    Your power jumpers look okay. As a quick test you can swap the SDA and SCL wires.

    If it does not work, try attaching a higher resolution photo of your board here, so we can have a look at it together.

      valor Hi! Thanks for your reply and the mini version.

      The length of wires between RPi and Mini-hub is about 30cm.

      I actually swapped SDA and SCL wires by accident and it prints following messages.

      and here is a high-resolution image of my hub.

        Well it looks like your accidental wire swap is the right one. Remember that please.
        Did you have all K_Ceptors connected when you got the errors "K_Ceptor setup error"?

          valor
          Hm... so pin3(SDA) on RPi goes to SLK on the hub and pin5(SLK) goes to SDA?

          I only have one K_Ceptor assembled so far.
          Whether it is connected or not, it prints the same error. 🙁
          I plugged a K_Ceptor to CH5 and tried the different channels but the same message(setup ERROR!).

            valor When I said all get positives, it meant the result of "i2cdetect -y 1"
            Is it normal?

                No, the SDA should go to SDA on RPI and SCL (what you call SLK) should go to SCL on RPI.
                Check my comment on the build thread: https://forum.chordata.cc/d/71-mini-k-ceptor-design/64

                You seem to have a shortcircuit on your U2 LTC4316 IC, and the solder job on the IMU looks a bit messy. Can you recheck how the pads are soldered?

                  valor The short-circuit on U2 doesn't matter. Those two pins are GND.
                  It looks messy because of the amount of flux I applied. I just cleaned it.

                  I followed the instruction on this thread(https://forum.chordata.cc/d/34-soldering-question) to solder IMU. It was harder than I expected. I may overheated the chip. Not sure how to check the solder under the chip though.

                  The problem here is my hub board, not the K-Ceptor(yet). I can't expect reliable results with it.
                  I will post the result once I assembled another Mini Hub board. Currently, I am waiting for the delivery of new components.

                      ChangyeobOk
                      That IMU is sitting way too skewed. Even if it's not the case, it takes time to eliminate each possible problem.
                      Usually it's always a lot easier if you build a few of each board. This way it might be easier to troubleshoot.

                          5 days later

                          ChangyeobOk When I said all get positives, it meant the result of "i2cdetect -y 1"
                          Is it normal?

                          No, it's an error on the bus. Most probably the SDA line is shorted with GND, but could also be something else.

                          Are you getting that result with no KCeptor connected? If so then you should focus on finding some soldering issue in the Hub first. Do you have a tester? you can test continuity between SDA and SCL, and also btw them and ground.
                          What happens if you unplug the Hub and run i2cdetect?

                          The solder bridges in the KCeptor @valor is pointing out will probably give you communication errors as well, but if understood the situation correctly they are not the cause of your current issue.

                              6 days later

                              daylanKifky I assembled another Mini-Hub
                              and it worked until I plugged a KC into #5. I think it was my KC that made my hub undetectable. But I don't exactly know how it happened.

                              I ordered my PCBs from JLC PCB and it came like this. See the two pads on U2 valor pointed out. They are already shorted before I solder them. Will it be a problem? Then I should ask them to send them again...
                              @valor Do your boards have shorted pads on U2?

                              valor I resoldered the IMU with hot air and it's sitting on the right spot. Still both 5v 3.3v red LEDs are on.

                              Question. If you connected a 6p6c cable into OUT on your KC, would it make your hub undetectable?
                              I checked my cable with a multimeter. All lines are good and it looks the same as your drawing. https://forum.chordata.cc/d/71-mini-k-ceptor-design/21

                                    ChangyeobOk yea, those two pads on U2 are actually supposed to be shorted. Sorry I draw attention to that, as it should not be a problem on your board.
                                    Connecting a 6p6c cable (with nothing on the other end) into the OUT connector on Mini K-Ceptor (or IN for that matter) should not have any effect at all.
                                    Connecting the Mini K-ceptor to a hub via IN or OUT connector should just work, since it's a shared bus. Direction labels "IN" and "OUT" are made for convenience and to ensure that the k-ceptors face the same direction thus the directions of the IMU data are consistent.
                                    On the Mini HUB, check the resistance between the VCC and all 6 pairs of SCLx and SDAx lines and make sure that you get around 10Kohm.

                                        valor Thanks for the clear explanation about IN/OUT connector! I was wondering about it.

                                        Only SCL3 reads 10.8k ohm and SCL6 is fluctuating between 68k. No readings for other points.
                                        I think:
                                        The chip looks it's soldered well but it is not.
                                        and/or
                                        I may overheated the chip while I was soldering with hot air.
                                        and/or
                                        I used old flux(it's brown color looks nasty) and the remaining flux affects the signal? I cleaned it with 91% isopropyl alcohol with a brush and a cotton swab though.

                                        Starting to feel frustrated...

                                            ChangyeobOk
                                            I assume you are measuring with the Mini Hub powered off.
                                            Do you have a microscope to check the solder joints thoroughly? You can always check for shorts on the neighboring pins which are not supposed to be shorted.
                                            Ugly old flux should not be a huge problem if it works. But if it's way past its age, it might not be wetting the pads well enough for the solder to pull.

                                            If you feel like the frustration is starting to build up, it might be a good idea to take a step back, maybe sleep on it. Tomorrow will be a fresher day for troubleshoting.