2.9.9. UART

AM62x integrates multiple 16C750-compatible UART modules in MAIN and MCU domains.

AM62x Starter Kit (SKEVM) has multiple UARTs routed to different connectors, as detailed in the table below.

UART	Connector	Notes
MAIN_UART0	USB MicroB Receptacle J15 via FT4232H chip	Linux console
MAIN_UART1		TIFS logging console
WKUP_UART0		DM logging console
MCU_UART0		MCU+ SDK M4 console

MAIN_UART0 is used as the Linux console, which is specified by the console option in kernel cmdline parameter.

root@am64xx-evm:~# cat /proc/cmdline
console=ttyS2,115200n8 earlycon=ns16550a,mmio32,0x02800000 mtdparts=fc40000.spi.0:512k(ospi.tiboot3),2m(ospi.tispl),4m(ospi.u-boot),256k(ospi.env),256k(ospi.env.backup),57088k@8m(ospi.rootfs),256k(ospi.phypattern) root=PARTUUID=d418f865-02 rw rootfstype=ext4 rootwait

UART initialization information is provided in the kernel boot log (dmesg). For example, to check which UART(s) are enabled in kernel:

root@am64xx-evm:~# dmesg | grep 'ttyS. '
[    0.296705] 2800000.serial: ttyS2 at MMIO 0x2800000 (irq = 18, base_baud = 3000000) is a 8250