OPT3001EVM Linux Getting Started Guide. Felipe Balbi

Transcription

1 OPT3001EVM Linux Getting Started Guide Felipe Balbi August 18, 2014

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3 Contents 1 Scope 1 2 Introduction OPT Beagle Bone Black Linux Kernel Hardware Platform 3 4 The Linux Kernel Writing Our DeviceTree Downloading The Correct Version Kernel Configuration Usage 13 6 Conclusion 15 ii

4 Chapter 1 Scope This document will describe the necessary steps to connect OPT3001EVM to a BeagleBone Black development platform. By the end of this User s Guide, the reader should be able to verify functionality of the OPT3001 device and get results from light measurements. 1

5 Chapter 2 Introduction 2.1 OPT3001 The OPT3001 is an ideal sensing device for measuring ambient light. Measurements can be made from 0.01 lux up to 83k lux without selecting full-scale ranges by using the built-in, full-scale setting feature. This capability allows light measurement over a 23-bit effective dynamic range. The spectral response of the ambient light sensor is tightly matched to the photopic response of the human eye and has significant infrared rejection. This tightly matched response offers accurate lux readings of different spectral sources, even under dark glass. The digital operation is flexible for system integration. Measurements can be either continuous or single-shot. The control and interrupt system features autonomous operation, allowing the processor to sleep while the sensor searches for appropriate wake-up events. The low power consumption and low power-supply voltage capability make this device ideal for battery-powered applications. 2.2 Beagle Bone Black Beagle Bone Black is an Open Source Hardware Software Development Platform using Texas Instruments AM335x System-on-Chip device. It provides an easy to use Software Development Platform based on an ARM Cortex-A8 CPU together with many other peripherals integrated into the die. 2.3 Linux Kernel The Linux Kernel was created by Linus Torvalds back in It s a General Purpose Operating System which works in many different architectures including, but not limited to, x86, ARM, ARC, Power, MIPS, and Alpha. 2

6 Chapter 3 Hardware Platform For the purpose of this Getting Started Guide, we will be using OPT3001EVM Rev B and Beagle Bone Black Rev A5C. The picture below shows a simple way of connecting OPT3001EVM to the Beagle Bone Black using a standard 100 mil spacing breadboard. Connected like that, OPT3001 will show on Beagle Bone Black s I2C Bus 2 1. The following section will describe all the necessary steps to get OPT3001 working on our Beagle Bone Black. Black 1 note that I2C Bus numbers start at 0, so I2C Bus 2 is the third I2C Bus on Beagle Bone 3

7 CHAPTER 3. HARDWARE PLATFORM 4 Figure 3.1: connecting opt3001evm to beagle bone black

8 Chapter 4 The Linux Kernel 4.1 Writing Our DeviceTree Now that we have OPT3001EVM connected to our Beagle Bone Black, we need to tell Linux about it. Recent Linux Kernel release utilize Open Firmware as the methodology for firmware to tell the Operating System about devices which sit under non-enumerable buses. The language used by Open firmware is known as DeviceTree With a DeviceTree source such as below, we can tell Linux that we have an OPT3001 device sitting under I2C Bus 2 and can be accessed through I2C address 0x44. /* arch/arm/boot/dts/am335x-boneblack.dts */ &i2c2 { status = "okay"; pinctrl-names = "default"; pinctrl-0 = <&i2c2_pins>; clock-frequency = <400000>; light@44 { status = "okay"; pinctrl-names = "default"; pinctrl-0 = <&light_pins>; compatible = "opt3001"; reg = <0x44>; }; }; interrupts-extended = <&gpio1 28 IRQ_TYPE_LEVEL_HIGH>; Note that we have two undefined pinctrl DeviceTree nodes. Let s define them: /* arch/arm/boot/dts/am335x-boneblack.dts */ 5

9 CHAPTER 4. THE LINUX KERNEL 6 &am33xx_pinmux { i2c2_pins: i2c2_pins { pinctrl-single,pins = < 0x178 (PIN_INPUT SLEWCTRL_FAST MUX_MODE3) /* uart1_ctsn.i2c2_sda */ 0x17c (PIN_INPUT SLEWCTRL_FAST MUX_MODE3) /* uart1_rtsn.i2c2_scl */ >; }; }; light_pins: light_pins { pinctrl-single,pins = < 0x78 (PIN_INPUT MUX_MODE7) /* gpmc_ben1.gpio1_28 */ >; }; 4.2 Downloading The Correct Version At the time of this writing OPT3001 driver is still not merged in the Mainline 1 Linux Kernel tree. Because of that we have provided git branches for all Linux Kernel versions starting with v3.14 all the way to v3.17. On each of those branches, you will find the same OPT3001 driver together with Beagle Bone Black devicetree changes for easy start. Depending on which Linux Kernel version you re using, download the correct branch as per table below: Linux Version GIT URL v3.14 git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git opt3001-v3.14 v3.15 git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git opt3001-v3.15 v3.16 git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git opt3001-v3.16 v3.17 git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git opt3001-v3.17 To download any of those branches a certain level of knowledge about the git version control system is required but the short version is below 2. $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git linux cloning into linux... remote: counting objects: , done. remote: compressing objects: 100% (582455/582455), done. remote: total (delta ), reused (delta ) receiving objects: 100% ( / ), mib 1.84 mib/s, done. resolving deltas: 100% ( / ), done. 1 Linux Kernel tree maintained by Linus Torvalds 2 we are assuming the reader already has git installed in their system

10 CHAPTER 4. THE LINUX KERNEL 7 checking connectivity... done. checking out files: 100% (47441/47441), done. $ cd linux $ git reset --hard opt3001-v Kernel Configuration After downloading the Kernel sources, we need to configure it for our setup. We will start by running: $ make ARCH=arm CROSS_COMPILE=arm-linux- omap2plus_defconfig hostcc scripts/basic/fixdep hostcc scripts/kconfig/conf.o shipped scripts/kconfig/zconf.tab.c shipped scripts/kconfig/zconf.lex.c shipped scripts/kconfig/zconf.hash.c hostcc scripts/kconfig/zconf.tab.o hostld scripts/kconfig/conf # # configuration written to.config # This first command will select all common configuration for Texas Instruments SoCs, including AM335x. Now we need to enable OPT3001 driver. For that, we will run: $ make arch=arm cross_compile=arm-linux- menuconfig You should see a screen such as below in Figure 4.1. After that, let s enable the industrial i/o framework and opt3001 driver, please follow the steps below and refer to the Screen Captures, if necessary. 1. navigate to Device Drivers and press ENTER (see figure 4.2); 2. navigate to Industrial I/O support (see figure 4.3); (a) press M 3 (see figure 4.4); or (b) press Y 4 (see figure 4.5); 3. navigate to Light sensors and press ENTER (see figure 4.6); 4. navigate to Texas Instruments OPT3001 Light Sensor (see figure 4.7); (a) press M (see figure 4.8); or (b) press Y (see figure 4.9); 3 M will compile a dynamically linked module 4 Y will link the binary statically to the kernel image

11 CHAPTER 4. THE LINUX KERNEL 8 5. exit menuconfig by following all Exit buttons; 6. when asked if you want to save the new configuration, choose Yes (see figure 4.10).

12 CHAPTER 4. THE LINUX KERNEL 9 Figure 4.1: linux kernel configuration main window Figure 4.2: Navigating to Device Drivers Figure 4.3: Navigating to Industrial I/O support

13 CHAPTER 4. THE LINUX KERNEL 10 Figure 4.4: Industrial I/O support after pressing M on the keyboard Figure 4.5: Industrial I/O support after pressing Y on the keyboard Figure 4.6: Navigating to Light sensors

14 CHAPTER 4. THE LINUX KERNEL 11 Figure 4.7: Navigating to Texas Instruments OPT3001 Light Sensors Figure 4.8: OPT3001 after pressing M on the keyboard Figure 4.9: OPT3001 after pressing Y on the keyboard

15 CHAPTER 4. THE LINUX KERNEL 12 Figure 4.10: Exitting menuconfig

16 Chapter 5 Usage After booting up and logging in to our Beagle Bone Black running Linux, we will navigate to the directory where files created by our OPT3001 Device Driver are located. To do that, please run: # cd /sys/bus/iio/devices/iio\:device0 # ls dev \verb in_illuminance_integration_time power events \verb integration_time_available subsystem \verb in_illuminance_input name uevent In order to get a single-shot Light measurement, all we have to do is read in_illuminance_input file. # cat \verb in_illuminance_input We can also setup thresholds and have events fire when such thresholds are reached. In order to illustrate that we will make use of iio_event_monitor, a tool which can be found at drivers/staging/iio/documentation/iio_event_monitor.c. Let s setup some thresholds: # cd events # ls \verb in_illuminance_thresh_falling_en \verb in_illuminance_thresh_falling_hysteresis \verb in_illuminance_thresh_falling_value \verb in_illuminance_thresh_rising_en \verb in_illuminance_thresh_rising_hysteresis \verb in_illuminance_thresh_rising_value # echo 200 > \verb in_illuminance_thresh_falling_value # echo 500 > \verb in_illuminance_thresh_rising_value # echo 1 > \verb in_illuminance_thresh_fallin_en # \verb iio_event_monitor /dev/iio\:device0 Event: time: , type: illuminance, channel: 0, evtype: thresh, direction: rising 13

17 CHAPTER 5. USAGE 14 Event: time: , type: illuminance, channel: 0, evtype: thresh, direction: falling Event: time: , type: illuminance, channel: 0, evtype: thresh, direction: rising Event: time: , type: illuminance, channel: 0, evtype: thresh, direction: falling Event: time: , type: illuminance, channel: 0, evtype: thresh, direction: rising Event: time: , type: illuminance, channel: 0, evtype: thresh, direction: falling

18 Chapter 6 Conclusion During this short Guide we have wired OPT3001EVM to a Beagle Bone Black using a standard breadboard, we downloaded and compiled the Linux Kernel and also verified that OPT3001 driver functions as expected. 15

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