AD5398
AD5398 Regulator Current Sink DAC Linux Driver.
Supported Devices
Evaluation Boards
Description
AD5398 and AD5821 is a single 10-bit DAC with 120mA output current sink capability. I2C bus is connected to enable/disable output and set the proper output current value. This driver adapts to voltage and current regulator framework in Linux kernel.
Source Code
Status
Files
Function |
File |
|---|---|
driver |
Adding Linux driver support
Configure kernel with make menuconfig (alternatively use make xconfig or
make qconfig)
Note
The AD5398/AD5821 Driver depends on CONFIG_I2C
Select voltage and current regulator framework support and enable AD5398/AD5821 driver. Don’t forget to select virtual regulator consumer and userspace regulator consumer as module. Because AD5398 driver is loaded after I2C bus finish initialization at kernel booting, built-in consumers may be loaded earlier and find supply in AD5398 driver is not available.
Linux Kernel Configuration
Device Drivers --->
[*] Voltage and Current Regulator Support --->
<M> Virtual regulator consumer support
<M> Userspace regulator consumer support
<*> Analog Devices AD5398/AD5821 regulators
Customize Device Parameters
The platform info defined in bf537-stamp board file is for ad5398 and ad5821 only. If you want to customize this driver for other compatible current regulator DAC, you should revise the platform information accordingly.
Define device supply name exported by the driver.
Define supply value range.
Define supply name in platform_data for the virtual consumer to match and use.
Define supply name for the user space consumer to match and use.
ad5398_bulk_data{} ad5398_userspace_comsumer_data{} ad5398_userspace_consumer_device{}
Driver Testing
Check regulator driver initialization information at kernel booting.
regulator: core version 0.5
i2c /dev entries driver
regulator: isink: 0 <--> 120 mA
ad5398 0-000c: ad5398 regulator driver loaded
i2c-bfin-twi i2c-bfin-twi.0: Blackfin BF5xx on-chip I2C TWI Contoller, regs_base@ffc01400
Check if AD5398 is probed properly.
root:/> ls -l sys/class/regulator/regulator.0/
lrwxrwxrwx 1 root root 0 Jan 1 19:47 device -> ../../../0-000c
-r--r--r-- 1 root root 4096 Jan 1 19:47 max_microamps
-r--r--r-- 1 root root 4096 Jan 1 19:47 microamps
-r--r--r-- 1 root root 4096 Jan 1 19:47 min_microamps
-r--r--r-- 1 root root 4096 Jan 1 19:47 name
-r--r--r-- 1 root root 4096 Jan 1 19:47 num_users
drwxr-xr-x 2 root root 0 Jan 1 19:47 power
-r--r--r-- 1 root root 4096 Jan 1 19:47 requested_microamps
-r--r--r-- 1 root root 4096 Jan 1 19:47 state
lrwxrwxrwx 1 root root 0 Jan 1 19:47 subsystem -> ../../../../../../../class/regulator
-r--r--r-- 1 root root 4096 Jan 1 19:47 suspend_disk_state
-r--r--r-- 1 root root 4096 Jan 1 19:47 suspend_mem_state
-r--r--r-- 1 root root 4096 Jan 1 19:47 suspend_standby_state
-r--r--r-- 1 root root 4096 Jan 1 19:47 type
-rw-r--r-- 1 root root 4096 Jan 1 19:47 uevent
root:/> cat sys/class/regulator/regulator.0/max_microamps
120000
root:/> cat sys/class/regulator/regulator.0/min_microamps
0
root:/> cat sys/class/regulator/regulator.0/name
current range
root:/> cat sys/class/regulator/regulator.0/type
current
root:/> cat sys/class/regulator/regulator.0/state
disabled
Insert virtual consumer driver module and check usability.
root:/> modprobe virtual
root:/> ls -l sys/devices/platform/reg-virt-consumer.0/
lrwxrwxrwx 1 root root 0 Jan 1 21:23 driver -> ../../../bus/platform/drivers/reg-virt-consumer
-rw-rw-rw- 1 root root 4096 Jan 1 21:23 max_microamps
-rw-rw-rw- 1 root root 4096 Jan 1 21:23 max_microvolts
-r--r--r-- 1 root root 4096 Jan 1 21:23 microamps_requested_current
-rw-rw-rw- 1 root root 4096 Jan 1 21:23 min_microamps
-rw-rw-rw- 1 root root 4096 Jan 1 21:23 min_microvolts
-r--r--r-- 1 root root 4096 Jan 1 21:23 modalias
-rw-rw-rw- 1 root root 4096 Jan 1 21:23 mode
drwxr-xr-x 2 root root 0 Jan 1 21:23 power
lrwxrwxrwx 1 root root 0 Jan 1 21:23 subsystem -> ../../../bus/platform
-rw-r--r-- 1 root root 4096 Jan 1 21:23 uevent
root:/> cat sys/devices/platform/reg-virt-consumer.0/max_microamps
120000
root:/> cat sys/devices/platform/reg-virt-consumer.0/min_microamps
0
root:/> echo 50000 > sys/devices/platform/reg-virt-consumer.0/min_microamps
root:/> cat sys/devices/platform/reg-virt-consumer.0/min_microamps
50000
root:/> cat sys/devices/platform/reg-virt-consumer.0/max_microamps
120000
Insert user space consumer driver module and check usability.
root:/> modprobe userspace-consumer
root:/> ls -l sys/devices/platform/reg-userspace-consumer.0/
lrwxrwxrwx 1 root root 0 Jan 1 21:26 driver -> ../../../bus/platform/drivers/reg-userspace-consumer
-r--r--r-- 1 root root 4096 Jan 1 21:26 microamps_requested_current
-r--r--r-- 1 root root 4096 Jan 1 21:26 modalias
-r--r--r-- 1 root root 4096 Jan 1 21:26 name
drwxr-xr-x 2 root root 0 Jan 1 21:26 power
-rw-r--r-- 1 root root 4096 Jan 1 21:26 state
lrwxrwxrwx 1 root root 0 Jan 1 21:26 subsystem -> ../../../bus/platform
-rw-r--r-- 1 root root 4096 Jan 1 21:26 uevent
root:/> cat sys/devices/platform/reg-userspace-consumer.0/name
ad5398
root:/> cat sys/devices/platform/reg-userspace-consumer.0/state
disabled
root:/> echo enabled > sys/devices/platform/reg-userspace-consumer.0/state
root:/> cat sys/devices/platform/reg-userspace-consumer.0/state
enabled
Tip
To control ADC to output a given current, you only need to set the value to sysfs entry min_microamps in virtual consumer platform device. The driver adjusts the output according to the min current value received.