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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.
| Function | File |
|---|---|
| driver | drivers/regulator/ad5398.c |
Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)
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 --->Virtual regulator consumer support Userspace regulator consumer support <*> Analog Devices AD5398/AD5821 regulators
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.
Check regulator driver initialization information at kernel booting.
This specifies any shell prompt running on the target
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.
This specifies any shell prompt running on the target
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.
This specifies any shell prompt running on the target
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.
This specifies any shell prompt running on the target
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
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.
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