Leonardo: serial output does not keep pace

Development Tools IDE 1.x
1

Hi all,
I have a small sketch that reads values from a led and writes them to the serial output. In the Serial Monitor they display just fine.

The output consists of a line number, a space and the value read.

To read them from the command line I first close the Serial Monitor. Then the problems begin.

'cat /dev/ttyACM0' only displays the first two lines and exits.
'tail -f /dev/ttyACM0' does the same and then nothing

'while head -1 /dev/ttyACM0 ; do : ; done' displays continuously, but skips every fifth or sixth line or so.

The same goes for 'while : ; do cat < /dev/ttyACM0 ; done'

I use Ubuntu, Bash and the last build of Arduino. Baudrate is set to 9600, which should not be too fast.

Any suggestions are welcome.

2

When you use the Leonardo's native USB connection the baud rate has no effect. The data is sent at full USB speed.

3

That is useful to know. but does dat explain the erratic behaviour?

4

paai:
Does that explain the erratic behavior?

I wouldn't think so but I could not be sure.

5

From the Leonardo data:

"The Leonardo differs from all preceding boards in that the ATmega32u4 has built-in USB communication, eliminating the need for a secondary processor. This allows the Leonardo to appear to a connected computer as a mouse and keyboard, in addition to a virtual (CDC) serial / COM port. It also has other implications for the behavior of the board; these are detailed on the getting started page"

I do not know anything about the Leonardo except what I have read, but I would think that the baud rate affects the USB port if it is simulating a virtual (CDC) serial/Com port. and the data is being sent serially over that virtual port. But, hey! I am very ignorant of the ability of that board.