Uart 4 can not open

We want to use three UARTs on our project. UART1 and UART2 we tried is ok.But when we use UART 4,it remind me,UART4 can not open. What we can do to deal with it ? Thank you.

The T20 / T30 have a limited amount of DMA ressources. May be, this could be the issue on your setup. Try once to disable DMA for some ports by setting “DmaSetting” to 0 in the registry. You find some more details on this developer webiste.

Thank you for you answer.I just resolve this question.After I add Serial4 to \Drivers\BuiltIn , I can use UART4. But I wonder why Alias T30 need to add. From the picture , UART4 is according to COM2 ,how to explain this appearance。325-无标题.png

There is a little mess with the namings of the devices. As Toradex wanted to have a module which is compatible with the namings to previous modules (Colibri PXA Family), we remapped the UARTS. So, UART_A/COM1 (Toradex Name) is UART 1 (Nvdia Name), UART B / COM2 (Toradex Name) is UART 4 (NVidia name) and so on.

I quickly checked again, if the table is still correct, and it is. COM 2 is still using the PINS called UART 4. Please be aware, that these pins are not configured until you open the port. This was different on images before 2.0 beta 1.