I have designed a circuit for wireless communication using an Xbee 900HP and a PIC16F1847 using UART. The circuit works and successfully sends data over UART, however when I scope the UART RX and TX lines I noticed some strange signals which are not large enough to cause any problems but are are none the less concerning as I have no explanation for them. Below I have attached images of the TX line of my PIC (RX line of the Xbee) with and without the Xbee attached to the circuit.
As you can see when the Xbee is attached there are some voltage “drops” in the TX line preceding my intended data signal. These drops look like digital data but i cannot be sure. Has anyone else experienced this or know of a possible reason?
For your reference I hav eattached a schematic of how the Xbee is wired to the PIC.
TX signal from PIC (UART) without Xbee attached
TX signal from PIC (UART) WITH Xbee attached
