device tree overlay for adxl345

-
experiment1:

 exporting device tree overlay and getting probe function called.

took this one as an example

/home/nikhil/bbblatest/bb.org-overlays/src/arm/BB-I2C2-00A0.dts

changed last lines as
// commented out example of a touchscreen (taken from BB-BONE-LCD7-01-00A4) */
adxl345@53 {
compatible = "adxl345";
reg = <0x53>;//chip ID of adxl345
//interrupt-parent = <&gpio4>;
//interrupts = <19 0x0>;
//atmel,irq-gpio = <&gpio4 19 0>;
};
};
};
};


renamed as BB-I2C2-ADXL-00A0.dts
compiled overlay as
dtc -I dts -O dtb -o BB-I2C2-ADXL-00A0.dtbo -b 0 -@ BB-I2C2-ADXL-00A0.dts
(before compiling i checked my dtc version, that was old. So updated from this directory/home/nikhil/bbblatest/bb.org-overlays and run dtc-overlay.sh. Now version is Version: DTC 1.4.4
)
copy the dtbo file in rootfs/lib/firmware folder

booted the board with sdcard.

cd /sys/devices/platform/bone_capemger

then cat slots
root@arm:/sys/devices/platform/bone_capemgr# cat slots
0: PF----  -1
 1: PF----  -1
 2: PF----  -1
 3: PF----  -1

then did this,

echo "BB-I2C2-ADXL" > slots 

now cat slots
root@arm:/sys/devices/platform/bone_capemgr# cat slots
 0: PF----  -1
 1: PF----  -1
 2: PF----  -1
 3: PF----  -1
 4: P-O-L-   0 Override Board Name,00A0,Override Manuf,BB-I2C2-ADXL

Also I got this print
root@arm:/sys/devices/platform/bone_capemgr# echo "BB-I2C2-ADXL" > slots
[  113.686287] bone_capemgr bone_capemgr: part_number 'BB-I2C2-ADXL', version 'N/A'
[  113.693901] bone_capemgr bone_capemgr: slot #4: override
[  113.699278] bone_capemgr bone_capemgr: Using override eeprom data at slot 4
[  113.712777] bone_capemgr bone_capemgr: slot #4: 'Override Board Name,00A0,Override Manuf,BB-I2C2-ADXL'
[  113.750647] #####Inside probe for adxl345
[  113.750647] 
[  113.766774] #####probe done for adxl345
[  113.766774] 
[  113.780934] bone_capemgr bone_capemgr: slot #4: dtbo 'BB-I2C2-ADXL-00A0.dtbo' loaded; overlay id #0

So the overlay worked.

experiment 2:
Installing overlay at boot up
changes need to be done in uEnv.txt






















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