How to normalize PWM signal from RX and TX serial lines
What I want to do now is get fancy and create LEDs that light up when the adapter is either sending or receiving data.


This implies peak detect and slow decay.
9600 baud is 960 char/s and a dwell time may be desirable from 0.1 to 1s by changing  1M to 10M (as shown.)







simulate this circuit &ndash; Schematic created using CircuitLab

Schematic fixed ( brain-phart)

With 50ohm driver in 74HCxxx @5V and 100nF RC=T=5us attack time.
 Good 'nuf.

It is possible to source 1mA current limited into ultrabright LEDs and load directly on Tx Rx.  The logic level threshold is same as TTL= 1.4V and LED needs at least 3 to 5V with 1k series which works for RS-232 ( but blinks )