Troubleshooting; Voltage Drop - sparkfun QwiicBus COM-18000 Hook-Up Manual

the devices are all connected together, power up the circuit. The photo below shows the QwiicBus assembled in
the default configuration (all boards powered with 3.3V) so your circuit may differ.
A completed QwiicBus Kit circuit using a SparkFun RedBoard Qwiic and operating at 3.3V
With everything adjusted and connected properly, that's all you need to assemble your QwiicBus circuit. Go forth
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and build ridiculously long, wired I C circuits to your heart's content!

Troubleshooting

Here a few troubleshooting tips for the SparkFun QwiicBus.
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I C Communication
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The PCA9615 supports I C clock speeds up to 1MHz at short distances but as the cable length increases, high
clock speeds can become more unreliable. If you find you are losing data or having unreliable communication on
your QwiicBus, try reducing the clock speed as a quick software fix. Switching to one of the alternate power
configurations can also help boost the reliability over long distances at high clock speeds.

Voltage Drop

Over long distances of cable the voltage may drop below the operating voltage range of the PCA9615 or attached
devices. The formula below can help you calculate the voltage drop at different lengths of CAT-5/Ethernet cable
and whether or not you will need to use one of the alternate power options:
I is the current through the object in Amperes and R is the resistance of the wires in Ohms. Most CAT-5/Ethernet
cable will have 24AWG internal wires and depending on the quality of the cable will be either copper or aluminum.
Refer to a table like this one from PowerStream to determine the resistance in Ω/1000ft or Ω/km to help calculate
the approximate voltage drop over your QwiicBus circuit.
Recommended Power-Up/Power-Down Procedure
Remember to power down the QwiicBus circuit before connecting or disconnecting any devices to the chain.
Connecting or disconnecting devices to the QwiicBus can damage the PCA9615 on the QwiicBus boards if it is
powered on.
Floating VDDB on the Terminating EndPoint
Reminder, when using any of the alternate power configurations, the 0-1 jumper on the primary / first EndPoint
should be OPEN but the 0-1 jumper on the terminating / last should be CLOSED to avoid leaving VDDB on the
terminating EndPoint floating. Take note that with the 0-1 jumper CLOSED, 5V is sent to the Qwiic connectors and