Strange issue on Raspberry Pi UART (with FTDI USB <--> RS-232 adapter)

ftdiraspberry piuart

I'm trying to establish a high speed UART communication on Raspberry Pi board. Since internal UART is not quite good at 1+ Mbaud, decided to use FTDI adapter (based on FT232RL chip) instead.

I've tested an adapter on my laptop running Debian 8 and reached stable transmission speed at 3 Mbaud (with a cat * >> /dev/ttyUSB0).
Then plugged it to Pi2 doing exactly the same, and noticed this:

(at 3 Mbaud)
enter image description here

(at 1 Mbaud)
enter image description here

There are wide (up to 1 second at 3 Mbaud) gaps in transmission at regular time intervals. Transmitting data is not corrupted, just delayed.
Any suggestion on how to overcome a problem? Thank you.

Best Answer

The RPi has only one USB Bus. One second long gaps sould be very rare, but you would see them if your data source for cat * uses the same USB bus to tranfer data into the RPi at the same time.

Something with more buffer like dd if=/dev/zero of=/dev/ttyUSB0 bs=1M should show less gaps, unless there are more USB devices active.

Related Topic