Module: XBee-3, Micro-Module
Firmware: DigiMesh 3002
Issue: Keeps resetting when UART Lines (RX) are left floating (DIO14)
I developed a custom board allowing to remote-control 16 PWM channels using a XBee-3 module. The modules have the latest (3002) DigiMesh Firmware installed and are running a Micro-Python Program at startup, which receives frames and set the PWM Channels according to the data in the Frame. The PWM itself is generated by a second IC and the XBee-3 is communicating with it using I2C.
I also mounted an FTDI IC on Board to allow on-board programming. When I remove the USB Port and power the module using a Battery, the XBee keeps resetting when a frame is received, approximatly every 5-6 seconds. In this case, both UART-Lines are switched to a connector using a MUX and they are left floating at the connector. So, when USB is connected, the MUX switches the UART-Lines to the FTDI chip instead of the connector.
I found out that, when i add a Pull-Up resistor on RX pin, everything is working fine. When left floating this pin stays IDLE low and may receive noise as no other UART receiver is connected.
So, are those Pull-Ups mandatory? Can I somehow activate an internal Pull-Up on the UART Pins?
I also would suggest, if that PULL-Up is mandatory in case of running micropython in a standalone-manner with no receiver present on the UART Lines, to mention that in the Hardware-Reference Manual.
Anyone had same experience?