Connecting several ESP32 in Master/Slave config using Serial Communication via Multiplexer.

[EdZamper]

Good afternoon Everyone,

I am trying to get 8 of the ESP32 devices connected via serial ports, in a Master/Slave configuration (using ESP32-WROOM-32U devices - 1 Master and 7 slaves). I have been able to share the TX line of the Master with all the Slave chips without issues, but now I need to share all the Tx lines of the slaves with the Master chip. I will handle the communication sync with software, however I am having issues to communicate each chip with the Master. I am using a MUX chip mounted on a Breakout device from Sparkfun, the BOB-09056 (CD74HC4067) https://www.sparkfun.com/products/9056 . This is a 16-in/1 out chip that Sparkfun says can communicate up to 16 Serial devices' TX lines to an RX line of a Master. Again, selection of the active channel is made via software on the ESP32 Master by controlling 4 selector bits. The EN is active LOW on the breakout and is grounded so it is always active, and the breakout is powered with a 5V PS, as well as the ESP32s. (all grounds tied to the same 5V power supply).
Right now I'm trying to connect only one device to the Master,, at a low baud setting (9600), using channel 0 on the breakout board, and I can see the signal through the SIG pin (using a LED only to test) which connects to the ESP32 Master but it does not appear to receive anything at its RX (Using TX0/RX0). As soon as I disconnect the TX of the Slave chip from the input of the MUX breakout board and connect it directly into the RX of the Master, the signal is received and acknowledged (a String message command) and the chip works correctly.

Has anyone used a MUX in this configuration? All the examples I've seen only seem to connect analog sensors to be read by the ESP32 (not Serial data ports). The Serial TX of the Slave ESP32 deliver digital signals @ 3.3V, and according to Sparkfun, it should be possible to get logical voltages using the 3.3V signals for serial comms. If someone can share and example of a MUX hardware configuration (schematic) to be able to read multiple Serial channels from various ESP32's, I'd appreciate it.

Thanks
-EZ