After reading the hookup guide of the endpoint connector, I’m a little confused with the power and jumper options on the QwiicBus-Endpoint (COM-16988). I’ve purchased a dozen of these endpoint extender for a project in which I need to run 40-meter cat-5 cables from an I2C sensor to an Arduino mega.
Here is my proposed connections:
On the primary endpoint (the one closest to the Arduino)
1- 5 volts from the Arduino will be connected to the VCC1 PTH.
2- GND from Arduino will connect to the GND PTH
3- SDA from Arduino will connect to SDA PTH
4- SCL from Arduino will connect to SCL PTH
On the secondary endpoint (the one closest to the Sensor)
1- VCC1 PTH will be connected to the sensors 5 volts in VCC in.
2- GND PTH will be connected to the sensors GND.
3- SDA PTH will be connected to the sensors SDA.
4- SCL PTH will be connected to the sensors SCL.
My questions are:
1- Are these connections acceptable
2- Do I need to open any bypass jumpers on either the primary or secondary endpoints? If yes which jumpers and which endpoints?
3- In this configuration, do I need to open one or both of the pull-up resistors jumpers
Hi, as I’m only connecting one sensor 40 meters from the microcontroller and don’t need to split the connection to another sensor, I was not aware that the mid-point was mandatory? Is the mid-point mandatory in all cases?
Hi, thanks for the feedback. Is this a configuration you have actually tried?
The reason I want to use the 5 volts config is that in the documentation, they seem to imply that 5 volts is better for longer distances.
This is from their hookup guide:“While the default 3.3V configuration should work just fine for shorter QwiicBus chains, we found the PCA9615 functions better when powered with 5V.”
I can see your point on the 0-1 jumper of the first board, but as I do not intend on attaching any other Qwiic devices to my last endpoint, I’m not sure its relevant in my case.
This is also from their hookup guide: “Also, It is also strongly recommended to OPEN the 0-1 jumper on the primary / first EndPoint to isolate VCC (VDDA) from VCC1 (VDDB) but leave the 0-1 jumper on the terminating EndPoint CLOSED. Leaving the 0-1 jumper closed will send 5V to any Qwiic devices attached to your terminating / last EndPoint.”
I’m still quite confused with how to implement these endpoints and hoping a sparkfun technical moderator can shed some light on this…
I’ve tried to get a hold of someone directly at Sparkfun support to get help on this and was told to post my question here and then informed that this was low priority for them as of May 31st. I really appreciate all the response I receive from the forum communities members, but have yet to here from a Sparkfun expert to help me resolved this… I’m hoping that this new post will catch someone attention and if not, then I guess I’ll have no other choice but to give up and move on…
If anyone at Sparkfun tech support sees this post, please respond…
In your case, both the Arduino mega and the sensor are 5V devices. Therefore, you want everything here running on 5V. Looking at the schematics, I would connect things as shown in your first post, and leave the 0-1 jumper connected.
Connecting 5v and gnd to the terminals near the RJ45 jack will send 5V power down the cable. Leaving 0-1 connected will also use that 5V to power the converter chip.
You will need to leave the I2C pullup jumper connected on the endpoint connected to the sensor. The Arduino mega has its own pullups on the I2C port, so I would cut the I2c pullup jumper on the endpoint(s) connected to the mega. You will likely be able to get away with leaving that jumper connected if you don’t have anything else with pullups connected to the i2c port on the mega
As for the warning about sending 5V to the quiic ports, that is not an issue if you aren’t using them and your sensor is 5V compatible
Thanks Mike, really appreciate your very helpful information.
Regarding the pullup resistors, makes sense that I open the pullup resistor on the Mega endpoint unit, regarding the endpoint connector at the sensor end, I just uncovered this from the Terra-Bee Evo-Mini I2C ToF sensor manual:
"Built-in pull-up resistors:10 kOhms on SDA and SCL (avoid additional pull-up resistors on the same bus to prevent transmission problems).
Based on this new info, would you concur that I should also open the pullup on the second endpoint since the sensor also has its own built-in pullup?
Yes, if the sensor has a pullup, you should open it on the endpoint (or the sensor; it doesn’t matter where the pullup lives on the bus - whichever is easier)
