I was following along the instructions, and I got to the point where I had to flash binaries to eMMC. The instructions say to connect the debug UART to a PC. How do I do this? From what I can see, the debug UART is just 4 holes, how am I supposed to connect this to my PC?
Thanks in advance!
If you solder the missing pins [1] you could route the four wires to a serial-USB connector - an example is this one [0].
Then plug the connector to one of the usb host ports of your computer (it should appear as a ttyUSBx).
On a linux hosts system you will probably want to modify /etc/udev/rules/99-usb.serial.rules as follows so that when udev detects the devices it creates a simlik (in the example below it would create /dev/96-hikey)
[jramirez@calypso ~]$ cat /etc/udev/rules.d/99-usb-serial.rules
SUBSYSTEM==“tty”, ATTRS{idVendor}==“0403”, ATTRS{idProduct}==“6001”, ATTRS{serial}==“FTXODWVO”, SYMLINK+=“96-hikey”
Then add a minicom configuration file to your home directory
[jramirez@calypso ~]$ cat .minirc.96-hikey
pu port /dev/96-hikey
pu parity L
pu rtscts No
You would start your console as below without having to worry about the device id.
$ minicom 96-hikey
note: if using UEFI, the console might be routed to the LS expansion (UART2 or UART3).
[0] 0403:6001 Future Technology Devices International, Ltd FT232 USB-Serial (UART) IC
[1] file:///home/jramirez/Downloads/HiKey_User_Guide_Rev0.2%20(1).pdf
If you check the 96 Boards specification (CE spec available from [1]) it says the following with respect to the UART:
One standard UART from the SoC shallbe made available for general purpose use on the low
speed expansion connector.
A second UART (TxD/RxD only) maybe made available on the low speed expansion
connector.
Note: Off the shelf FTDI 1.8V serial USB cables may be used to interface to these interfaces
Actually, if your are going to use UEFI, then you dont need to solder any pins.
If you look at the grub.cfg [1] file embedded in the boot.img, you can see that it uses AMA3 which is accessible from the LS expansion connector
