Hi,
I’m using a aml-s805x-ac running raspbian. I’m trying to activate the i2c bus on pin 27 and pin 28 of the 40 pin header to commucicate with an other device over i2c. So far I haven’t been sucessful. Does anyone know how to active an use the i2c bus on the aml-s805x-ac?
Thanx for the help!
Have you tried applying the I2C-b overlay ?
There is one in the Library for the 805 from what I can see !
yes i applied the i2c-b overlay with the libretech wiring tool. It also show the meson i2c adapter on i2c-1 afterwards. But when i what to check the device adress of my i2c device I don’t see anything. do you know why the device is not detected? Im sure i have wired anything to the right pins…
thx for the help
Looks like it should be there ! Just make sure you have the SDA & SCL connected to the right pins.
What device are you trying to connect ?
Have you tried another i2c device ?
Also you could try i2c-ao and pins 3&5 ?
I checked the wiring several times, so I’m pretty sure it should be wired the right way.
I try to connect temperature measuring shield (RTD Data Acquisition 8-Layer Stackable HAT for Raspberry Pi).
Yes I just tried to connect a raspberry to the bus. But the same problem occures that the libre computer doesn’t detect any device
I also tried the i2c-ao but I’m not sure if the AML-S805X-AC (La Frite) support i2c functions at the pins 3 and 5. If you look at the pin out i2c function are not listed at pin 3 and 5 (AML-S805X-AC-V1.0A/B Headers - Google Tabellen)
I agree drawing doesn’t show but as its an official overlay I assume its correct.
I would try a I2C device with just 4 pins V,Gnd,SDA & SCL (Tiny .96"OLED or shift registers are always useful & cheap) first to validate the functionality and you can always try swapping around your SDA & SCL connections just to make sure if not successful at first. You should be able to make the device work on both I2C ports after enabling appropriate overlay.
The pull-up for I2C might not be enabled. Does i2c-detect show every address?
Not sure. I have never done anything about the pull ups. But when I look on the lines with an scope one of the lines gets pulled up to 3.3v. however how would i enable the pullups if they are not already enabled?
The only adress that the i2c-detect shows is on i2c-0 (DesignWare HDMI). I’m not sure thats the right one. On the i2c-1 and i2c-2 which I activated, it doesn’t show anything. Even if i connect varoius i2c devices.
Do you have any idea why?
If you are on AML-S805X-AC, you need to use i2c-gpio as pin 3 and 5 are not hardware I2C per the schematic: GPIO Pin Header Maps and Wiring Tool for Libre Computer Boards
I am able to get I2C to work on pin 27 and 28 (on La Frite) by using and modifying i2c-b.dts. According to the spreadsheet pins 27 and 28 are GPIODV 24 and 25. And these two are i2c_A instead of i2c_B.
Open i2c-b.dts for aml-s805 (path: libretech-wiring-tool/libre-computer/aml-s805x-ac/dt/i2c-b.dts).
Modify these:
/*
/*
/dts-v1/;
/plugin/;
/ {
compatible = “libretech,aml-s805x-ac”, “amlogic,s805x”, “amlogic,meson-gxl”;
fragment@0 {
target-path = "/aliases";
__overlay__ {
i2c2 = "/soc/cbus@c1100000/i2c@87c0";
};
};
fragment@1 {
target = <&i2c_a_pins>;
__overlay__ {
cfg {
pins = "GPIODV_24", "GPIODV_25";
bias-pull-up;
};
};
};
fragment@2 {
target = <&i2c_A>;
__overlay__ {
status = "okay";
pinctrl-0 = <&i2c_a_pins>;
pinctrl-names = "default";
};
};
};
We have updated the overlays for AML-S805X-AC. We will add the I2C pull up into the next firmware update.