We are using MiFi along with several of the GPIOs for a project and noticed something strange recently. On power up, the Mifi will turn on GPIO 15 for a few seconds, and then once UBoot hands off to OpenWRT to boot the GPIO goes off again.

Now I swear MiFis that we ordered 6 months ago did not do this, but perhaps I just never noticed it… anyway I downloaded the AR150/MiFi/Domino UBoot from GL-Inet github to see what was going on, and after some digging finally found these lines in “u-boot/common/main.c”:

        //add start by gl-inet_xiaoxin
        gpio_control(GPIO_13_INDICATE_POWER,GPIO_13_ON);// This led is indicate power on
        gpio_control(GPIO_6_ENABLE_USB,GPIO_6_ON);// This gpio is enable usb
        //add end by gl-inet_xiaoxin

The definition pulled in from the Makefile for domino sets:

#define GPIO_6_ENABLE_USB                    6
#define GPIO_6_ON                            1
#define GPIO_13_INDICATE_POWER              15
#define GPIO_13_ON                           1

On the AR150 GPIO 15 is used for the the Power LED, so this makes sense; however on MiFi this GPIO is left available for user access.

So I have rebuilt Uboot with GPIO_13_ON set to 0, so that uBoot will not turn the GPIO on. The build looks OK, but I am nervous that something may not be right and I will end up bricking my unit… so:
a) Does MiFi have any kind of JTAG interface/support in case my build is bad??
b) Does anyone have such a JTAG interface hooked up and willing to test my uboot build???

MiFi uses the same uboot as AR150 so this is the problem.

MiFi doesn’t have jtag. So if you flash the wrong uboot it will brick your device.

@alzhao That’s what I was afraid of.

Any chance that a GL Staff member could rebuilt a u-boot image for MiFi specifically that has GPIO_13_ON set to 0 instead of 1? Only a single line of code needs to be changed:
Line 516 in “https://github.com/gl-inet/uboot-source-for_ar150_mifi_domino/u-boot/Makefile

        @echo "#define GPIO_13_ON                           0" >> include/config.h

then make clean; make domino and should be all good. You guys already have 3 binary images in the bin/ folder of that repository, so it would be easy enough to simply replace the existing uboot-gl-mifi.bin with the newly generated one, and leave the AR150 image alone…

Let me know if that is feasable… otherwise I will have to just close my eyes and potentially sacrifice 1 MiFi in the name of testing…

Well what you can do is get one of those eeprom clamps, dump the eeprom using it as a backup. Then if you brick the device you can restore the uboot.

@kyson-lok pls help to get a working uboot for mifi.

The system led for MIFI isn’t user controllable, it isn’t use GPIO15, while GPIO15 is user controllable. What you do is correct. I rebuilt a u-boot for you without turn on GPIO15. Please unzip the attachment.

uboot-gl-mifi.zip (59.5 KB)

@kyson-lok Awesome thank you, this solved the problem for us and lets GPIO 15 remain for use by our application without worrying about bootloader doing strange things to it!