Use the io command to check pin multiplexing

The following is a description of 3368 UART3 flow control

 

1. First look at the schematic diagram and find the pin definition

 

2.  Open the instruction manual of the chip and find the GPIO3_C0 GPIO3_C1

Find the GRF chapter and get the IOMUX offset address of the GPIO group , as follows: 0x0028

 

3. View the base address

You can see that the GRF starting base address is 0xFF770000

So the address of this GPIO3_C group is 0xFF770028

So use io -4 -r 0xFF770028 to get the value of this register

According to the obtained register value, it can be checked whether the multiplexing is abnormal or not.

Note:

If the following exception occurs when reading

 

rk3368H_64:/ # io -4 -r 0xFF770028                                                                                                      

open /dev/mem: No such file or directory

1|rk3368H_64:/#

needs to be enabled in the kernel

CONFIG_DEVMEM=y

CONFIG_DEVKMEM=y