Life is full of electromagnetic waves of various wavelengths. The so-called visible (color) light is the electromagnetic spectrum visible to the human eye. Its wavelength is 380~770nm. In order to avoid the light emitted by the remote control from causing discomfort to the human eye and reduce the interference of general artificial light sources, Therefore, the infrared (Infrared) wavelength invisible to the human eye is selected. At present, almost all remote control emitters in the industry use a wavelength of 940nm.
The application of infrared remote control is also a kind of wireless signal transmission. Like most wireless transmission technologies, in order to avoid the interference of electromagnetic waves of the same wavelength in the environment, a carrier frequency (carrier frequency) as shown in the figure below will be added to the transmission signal. , the carrier range in remote control applications is 30~60kHz, and 38kHz is the most common carrier frequency.
Currently, infrared remote control protocols include RC5, SIRCS, Sy, RECS80, Denon, NEC, Motorola, Japanese, SAMSWNG and Daewoo, etc. Rockchip平台只支持 NEC 编码, most domestic electrical appliances use this encoding protocol.
RK platform PWM has three working modes, reference mode, one-shot mode and continuous mode. The infrared remote control uses reference mode. In this mode, the PWM can capture the width of the input high and low levels and generate an interrupt. After receiving the interrupt, the CPU goes to The corresponding register is read.
1. Refer to the schematic diagram to add the configuration of the kernel IR
1.1 Add the following configuration to the device tree in use:
&pwm3 {
status = "okay";
compatible = "rockchip,remotectl-pwm";
remote_pwm_id = <3>;
handle_cpu_id = <1>;
remote_support_psci = <0>;
pinctrl-names = "default";
pinctrl-0 = <&pwm3_pins>;
ir_key1 {
rockchip,usercode = <0x4040>;
rockchip,key_table =
<0xf2 KEY_REPLY>,
<0xba KEY_BACK>,
<0xf4 KEY_UP>,
<0xf1 KEY_DOWN>,
<0xef KEY_LEFT>,
<0xee KEY_RIGHT>,
<0xbd KEY_HOME>,
<0xea KEY_VOLUMEUP>,
<0xe3 KEY_VOLUMEDOWN>,
<0xe2 KEY_SEARCH>,
<0xb2 KEY_POWER>,
<0xbc KEY_MUTE>,
<0xec KEY_MENU>,
<0xbf 0x190>,
<0xe0 0x191>,
<0xe1 0x192>,
<0xe9 183>,
<0xe6 248>,
<0xe8 185>,
<0xe7 186>,
<0xf0 388>,
<0xbe 0x175>;
};
......
};
1.2 Check the input device and find the pwm infrared device just added. The driver is loaded normally, and the next step is to add the remote control according to the key value.
\> adb shell
rk3568_r:/ # getevent
add device 1: /dev/input/event3
name: "Logitech USB Optical Mouse"
add device 2: /dev/input/event2
name: "WDR USB Camera: WDR USB Camera"
add device 3: /dev/input/event0
name: "fdd70030.pwm"
add device 4: /dev/input/event1
name: "rk805 pwrkey"
add device 5: /dev/input/event4
name: "adc-keys"
add device 6: /dev/input/event5
name: "rk-headset"
2. Add the infrared button to report the key value (defined separately by the rk platform)
The rk platform can directly view the infrared receiver, and the command to open the key value is as follows:
echo 1 > /sys/module/rockchip_pwm_remotectl/parameters/code_print
There are too many kernel logs, you can use the adb command (or serial port printing) to filter and get the key value directly, USERCODEadd the rockchip and usercode corresponding to the remote control dts, and RMC_GETDATAthe corresponding key value can be converted to the rk-input key value through rockchip, key_table.
adb root;adb shell
# cat /dev/kmsg | grep USERCODE -A 2
6,1136,469064745,-;USERCODE=0x4040
6,1137,469091760,-;RMC_GETDATA=b2
6,1138,482889791,-;USERCODE=0x4040
6,1139,482916765,-;RMC_GETDATA=b4
Letter and symbol keys are standard key values of linux, which can kernel/include/dt-bindings/input/linux-event-codes.hbe viewed in the file.
3. Add key-value transformation
The Linux standard key value is not the same as the Android standard key value, and it is necessary to convert the file to match the corresponding relationship. The intermediate conversion configuration file will use PWM to match the configuration file corresponding to the name of the PWM label according to the infrared remote control. This debugging uses the number pwm3 corresponding to PWM3: pwm@fdd70030 {, the name of the key-value conversion configuration file fdd70030_pwm.kl, and the device description file is fdd70030_pwm.idc.
If you don't understand the Android key value, you can view
frameworks/base/core/java/android/view/KeyEvent.javathe file;
you can manually copy it for temporary debugging/vendor/usr/keylayout, and restart it to take effect.
fdd70030_pwm.idc
device.internal = 1 #是否为内部设备
audio.mic = 0 #是否带mic
dd70030_pwm.kl
key 116 POWER
key 102 HOME
key 139 MENU
key 113 VOLUME_MUTE
key 115 VOLUME_UP
key 114 VOLUME_DOWN
key 158 BACK
key 232 DPAD_CENTER
key 103 DPAD_UP
key 108 DPAD_DOWN
key 105 DPAD_LEFT
key 106 DPAD_RIGHT
key 240 PROFILE_SWITCH
key 15 TAB
key 104 PAGE_UP
key 109 PAGE_DOWN
key 2 1
key 3 2
key 4 3
key 5 4
key 6 5
key 7 6
key 8 7
key 9 8
key 10 9
key 11 0
key 52 PERIOD
key 111 DEL
key 119 MEDIA_PAUSE
key 207 MEDIA_PLAY
key 418 F3
key 419 F4
4. Automatically compile and build
Need to copy fdd70030_pwm.kl and fdd70030_pwm.idc to device/rockchip/commonthe directory. And add copy rules in device.mk, it will be automatically copied to the specified directory when compiling.
PRODUCT_COPY_FILES += \
device/rockchip/common/fdd70030_pwm.kl:system/usr/keylayout/fdd70030_pwm.kl \
The power button has no effect during debugging.
Theoretically, after the usercode and keycode are added, the system needs to 重新启动use the power button once. (At this time, after rebooting, look at the keycode value printed by the serial port, and directly replace the previous powerkey_keycode value with the u-boot stage code), which can achieve the effect that the power key can be used for the first time when the power key is burned.
Note:
a) "OK" key is KEY_REPLY.
b) /vendor/usr/keylayout is the same as /system/usr/keylayout.
c) Infrared registration failed, you can check PWM GPIO multiplexing (iomux).