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 ---> <M> Virtual regulator consumer support <M> 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.
<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:ad5398_consumer{} c linux-kernel>
<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:ad5398_regulator_data{} c linux-kernel>
<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:ad5398_virt_consumer_device{} c linux-kernel>
<source trunk/arch/blackfin/mach-bf537/boards/stamp.c:ad5398_bulk_data{} c linux-kernel> <source trunk/arch/blackfin/mach-bf537/boards/stamp.c:ad5398_userspace_comsumer_data{} c linux-kernel> <source trunk/arch/blackfin/mach-bf537/boards/stamp.c:ad5398_userspace_consumer_device{} c linux-kernel>
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.