Problems with Full Duplex Serial

rcm14

Whenever I call the full duplex serial object for my project, for some reason, it outputs a constant HIGH until I say to send some code. It used to be LOW until I sent the information through it. This is a very recent problem I am having and have no clue where to start to fix it.

Any help would be appreciated.

Mike Green

All serial drivers send a constant HIGH when not sending data. This is normal. Any asynchronous serial signal will idle at HIGH. The start bit goes LOW, then the data bits are HIGH or LOW, then the stop bit goes HIGH and stays HIGH until the next start bit.

What may be happening is that the signal line is LOW until the serial driver (FullDuplexSerial) finishes initializing itself. Note that there's a mode parameter to the .start method and one of the mode bits specifies inverted transmit mode. This inverts the HIGH / LOW output of the driver and the signal line will idle at LOW. All the bits will be inverted as well ... start bit, data bits, and stop bit. This may be what you want. If you're using FullDuplexSerial for receiving as well, you will want to set the invert receive mode bit too.

Inverted mode is often used when interface circuitry already has an inverter.