Hi,
I need to connect about 500 proximity sensors (Proximity Sensor Breakout - 20cm, VCNL4040 ) to build an array-like system. Is it possible to connect this large no. of sensors to Arduino with the help of SparkFun Qwiic Mux Breakout - 8 Channel (TCA9548A). I appreciate any help you can provide.
Best,
Nilanjan
The VCNL4040 has a fixed address - 0x60. Therefore, you can only put one on each port of the TCA9548A. This will let you access 8 of them. The TCA9548A has 8 available addresses, but you can’t reuse those addresses if you connect TCA9458A’s in series, since you wouldn’t be able to talk to the ones further down the chain. So for the first TCA would drive 7 TCA’s, each would then drive 6 TCA’s. At this point, you have enough ports for 768 = 310 VCNL. You would need to add one more rank to get enough ports for 500 VCNL.
This isn’t taking into account the issues of wiring, power (the LEDs pulse at 200mA, though you can set it lower) and are asynchronous so you will need enough capacitance at each one to supply this surge current) and the time it will take to talk to all of those muxes and sensors and process the data.
I would probably look at using multiple Arduinos sharing a common bus (RS422 or RS485 comes to mind) with each handling a subset of the sensors. This will reduce the workload on the Arduino and the number of muxes. If you are ok with software (bit-banging) i2c, which would be a bit slower, you could have three Arduino Mega 2560, each with 21 software i2c busses. Each bus would have one mux, allowing for 200 VCNL on each.
Using UNOs, you could bit-bang 8 i2c ports allowing for 64 sensors after one rank of muxes. 8 of these would handle the 500 sensors; this is probably the best bet if the Arduino is fast enough for your application.
/mike