ADP1650

ADP1650 LED Flash Linux Driver.

Supported Devices

Evaluation Boards

Description

The ADP1650 is a programmable LED driver designed for camera flash applications in mobile devices. It provides current regulation up to 1.5 A for high-current flash mode and adjustable torch mode operation, with I2C programmability and hardware strobe input for precise timing control.

Source Code

Status

Source

Mainlined?

git

In Progress

Files

Function

File

driver

drivers/leds/leds-adp1650.c

include

include/linux/i2c/adp1650.h

Example platform device initialization

For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.

For devices on custom boards, as typical of embedded and SoC-(system-on-chip) based hardware, Linux uses platform_data to point to board-specific structures describing devices and how they are connected to the SoC. This can include available ports, chip variants, preferred modes, default initialization, additional pin roles, and so on. This shrinks the board-support packages (BSPs) and minimizes board and application specific #ifdefs in drivers.

Note

platform_data: Platform data specific to the ADP1650 device. Includes feature selections and default initialization.

Please see include/linux/i2c/adp1650.h for details.

#include <linux/i2c/adp1650.h>

static struct adp1650_leds_platform_data adp1650_pdata = {
    .timer_iocfg =  ADP1650_IOCFG_IO2_HIGH_IMP |
            ADP1650_IOCFG_IO1_TORCH |
            ADP1650_FL_TIMER_ms(500),

    .current_set =  ADP1650_I_FL_mA(900) |
            ADP1650_I_TOR_mA(100),

    .output_mode =  ADP1650_IL_PEAK_2A25 |
            ADP1650_STR_LV_EDGE |
            ADP1650_FREQ_FB_EN |
            ADP1650_OUTPUT_EN |
            ADP1650_STR_MODE_HW |
            ADP1650_STR_MODE_STBY,

    .control =  ADP1650_I_TX2_mA(400) |
            ADP1650_I_TX1_mA(400),

    .ad_mode =  ADP1650_DYN_OVP_EN |
            ADP1650_STR_POL_ACTIVE_HIGH |
            ADP1650_I_ILED_2mA75 |
            ADP1650_IL_DC_1A50 |
            ADP1650_IL_DC_EN,

    .batt_low = ADP1650_CL_SOFT_EN |
            ADP1650_I_VB_LO_mA(400) |
            ADP1650_V_VB_LO_3V50,

    .gpio_enable = -1,
};

Unlike PCI or USB devices, I2C devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each I2C bus segment, and what address these devices are using. For this reason, the kernel code must instantiate I2C devices explicitly. There are different ways to achieve this, depending on the context and requirements. However the most common method is to declare the I2C devices by bus number.

This method is appropriate when the I2C bus is a system bus, as in many embedded systems, wherein each I2C bus has a number which is known in advance. It is thus possible to pre-declare the I2C devices that inhabit this bus. This is done with an array of struct i2c_board_info, which is registered by calling i2c_register_board_info().

So, to enable such a driver one need only edit the board support file by adding an appropriate entry to i2c_board_info.

For more information see: How to instantiate I2C devices

static struct i2c_board_info __initdata board_i2c_board_info[] = {
#if defined(CONFIG_LEDS_ADP1650) || defined(CONFIG_LEDS_ADP1650_MODULE)
    {
        I2C_BOARD_INFO("adp1650", 0x30),
        .platform_data = (void *)&adp1650_pdata,
    },
#endif
};

static int __init board_init(void)
{
    [--snip--]

    i2c_register_board_info(0, board_i2c_board_info,
                ARRAY_SIZE(board_i2c_board_info));
    [--snip--]

    return 0;
}
arch_initcall(board_init);

Adding Linux driver support

Configure kernel with make menuconfig (alternatively use make xconfig or make qconfig)

Tip

The ADP1650 LED driver depends on I2C.

Device Drivers  --->
    [] LED Support  --->
        --- LED Support
        []   LED Class Support
             LED drivers

        <--snip-->
        <>   LED Support for ADP1650 I2C chips
        <--snip-->

Driver testing

LED handling under Linux

The LED class allows control of LEDs from userspace. LEDs appear in /sys/class/leds/. The brightness file will set the brightness of the LED (taking a value 0-255).

For more information read linux/Documentaion/leds-class.txt

; **brightness** : get/set LED brightness (an integer between 0 and 255)
; **max_brightness** : the maximum brightness value.

Driver specific brightness interpretation

Value

Define

Description

Intensity

0

FL_MODE_OFF

Turns LED/FLASH off

0

1

FL_MODE_TORCH_25mA

Software initiated TORCH/Assist light

25mA

2

FL_MODE_TORCH_50mA

(STROBE) triggers FLASH

50mA

3

FL_MODE_TORCH_75mA

75mA

4

FL_MODE_TORCH_100mA

100mA

5

FL_MODE_TORCH_125mA

125mA

6

FL_MODE_TORCH_150mA

150mA

7

FL_MODE_TORCH_175mA

175mA

8

FL_MODE_TORCH_200mA

200mA

9

FL_MODE_TORCH_TRIG_EXT_25mA

Hardware (GPIO1) triggered TORCH/Assist light

25mA

10

FL_MODE_TORCH_TRIG_EXT_50mA

(STROBE) triggers FLASH

50mA

11

FL_MODE_TORCH_TRIG_EXT_75mA

75mA

12

FL_MODE_TORCH_TRIG_EXT_100mA

100mA

13

FL_MODE_TORCH_TRIG_EXT_125mA

125mA

14

FL_MODE_TORCH_TRIG_EXT_150mA

150mA

15

FL_MODE_TORCH_TRIG_EXT_175mA

175mA

16

FL_MODE_TORCH_TRIG_EXT_200mA

200mA

254

FL_MODE_FLASH

Software initiated LED FLASH

I_FL

255

FL_MODE_FLASH_TRIG_EXT

Hardware (STROBE) triggered LED FLASH

I_FL

Example LED usage

root:/> cd sys/class/leds/adp1650/

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> ls -l
-rw-r--r--    1 root     root          4096 Jan  5 08:42 brightness
lrwxrwxrwx    1 root     root             0 Jan  5 08:23 device -> ../../../0-0030
-r--r--r--    1 root     root          4096 Jan  5 08:23 max_brightness
drwxr-xr-x    2 root     root             0 Jan  5 08:23 power
lrwxrwxrwx    1 root     root             0 Jan  5 08:23 subsystem -> ../../../../../../../class/leds
-rw-r--r--    1 root     root          4096 Jan  5 08:23 uevent
Enable TORCH/Assist Light (Intensity 100mA)

Note

A subsequent assert of STROBE will trigger the FLASH

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 4 > brightness
Prepare TORCH/Assist Light for an GPIO1 enable trigger (Intensity 100mA)

Note

A subsequent assert of STROBE will trigger the FLASH

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 12 > brightness
Initiate FLASH (Intensity set by I_FL)
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 254 > brightness
Prepare FLASH for an STROBE triggered enable (Intensity set by I_FL)
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 255 > brightness
Disable all LED activity
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 0 > brightness

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