Computing stuff tied to the physical world

UartPlug class

In AVR, Hardware, Software on Dec 20, 2009 at 00:01

Here is a utility class for the UART Plug:

Screen shot 2009-12-18 at 13.42.26.png

The interface is exactly the same as the Serial class, so it can be used interchangeably. Here is the updated “uart_demo” example in the Ports library:

Screen shot 2009-12-18 at 13.38.44.png

Here’s a test setup with a second JeeNode running RF12demo plugged in:


Sample output:

Screen shot 2009-12-18 at 13.38.29.png

Both input and output are supported by this UartPlug class – this demo is essentially a serial pass-through.

The UART supports accurate baud rates all the way up to 230400, which is in fact beyond the current I2C rates of the Ports library. Even at 57600 baud, I’ve seen several serious overruns with the above demo. One reason is that it’s only reading out one byte at the time, going through a multi-byte I2C bus sequence for each one (!). Note also that the Serial class does not buffer its output, so it can easily bog down everything else.

The UART hardware can support both hardware handshaking and XON/XOFF throttling, so this would be another way to avoid buffer overruns.

Up to say 9600 baud the UartPlug class should work fine, even with several UART plugs on the same I2C bus.