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DAC Linux driver
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== Article purpose == 本文介绍了用于DAC driver for the DAC<ref name="DAC internal peripheral">[[DAC internal peripheral]]</ref> 内部外围设备的Linux<sup>®</sup>驱动程序: * 驱动程序支持哪些DAC功能 * 如何配置,使用和调试驱动程序 * 驱动程序的结构是什么,以及在哪里可以找到源代码 == Short Description == DAC Linux<sup>®</sup> 驱动程序(内核空间)基于 [[IIO overview|IIO]] 框架。 它实现了'''IIO直接模式''',以在每个通道上独立执行单个转换。<br/> == Configuration == === Kernel configuration === Activate the DAC<ref name="DAC internal peripheral"/> Linux<sup>®</sup> driver in the kernel configuration using the Linux Menuconfig tool: [[Menuconfig or how to configure kernel]] (enable CONFIG_STM32_DAC). <pre> Device Drivers ---> <*> Industrial I/O support ---> Digital to analog converters ---> <*> STMicroelectronics STM32 DAC </pre> === Device tree === Refer to the [[DAC device tree configuration]] article when configuring the DAC Linux kernel driver. == How to use == In "IIO direct mode", conversions can be done directly via sysfs. See [[How to use the IIO user space interface#How to do a simple DAC conversion using the sysfs interface|How to do a simple DAC conversion using the sysfs interface]]. == How to trace and debug == Refer to [[IIO_overview#How_to_trace_with_dynamic_debug|How to trace with dynamic debug]] for how to enable debug logs in the driver and in the Framework. Refer to [[IIO_overview#How_to_debug_with_debugfs|How to debug with debugfs]] for how to access the DAC registers. The DAC has system wide dependencies towards other key resources: * '''runtime power management''' can be disabled, for example it may be forced '''on''' via ''power/control'' sysfs entry: {{Board$}} cd /sys/devices/platform/soc/40017000.dac/40017000.dac\:dac@1/ {{Board$}} cat power/autosuspend_delay_ms 2000 {{Board$}} cat power/control auto # kernel is allowed to automatically suspend the ADC device after autosuspend_delay_ms {{Board$}} {{highlight|echo on > power/control}} # force the kernel to resume the DAC device (e.g. keep clocks and regulators enabled) {{Info| It might be useful to disable runtime power management, in order to dump registers by any means or to check clock and regulator usage (see example below).}} * '''clock'''<ref name="Clock overview">[[Clock overview]]</ref> usage can be verified by reading ''clk_summary'': {{Board$}} {{highlight|cat /sys/kernel/debug/clk/clk_summary}} | grep dac dac12_k 0 0 0 32000 0 0 dac12 1 2 0 98303955 0 0 * '''regulator'''<ref name="Regulator overview">[[Regulator overview]]</ref> tree and usage usage can be verified (e.g. use count, open count and regulator reference voltage) as follows: {{Board$}} {{highlight|cat /sys/kernel/debug/regulator/regulator_summary}} regulator use open bypass voltage current min max ------------------------------------------------------------------------------- v3v3 4 5 0 3300mV 0mA 3300mV 3300mV vdda 1 2 0 2900mV 0mA 2900mV 2900mV 40017000.dac 0mV 0mV 48003000.adc 0mV 0mV * '''pinctrl'''<ref name="Pinctrl_overview">[[Pinctrl overview]]</ref> usage can be verified by reading ''pinmux-pins'': {{Board$}} cd /sys/kernel/debug/pinctrl/soc\:pin-controller@50002000/ {{Board$}} {{highlight|cat pinmux-pins}} | grep dac pin 4 (PA4): device 40017000.dac function {{highlight|analog}} group PA4 pin 5 (PA5): device 40017000.dac function {{highlight|analog}} group PA5 # check pins are assigned to DAC and configured as "analog" == Source code location == The DAC source code is composed of: * {{CodeSource | Linux kernel | drivers/iio/dac/stm32-dac-core.c | stm32-dac-core driver}} to handle common resources such as [[Clock overview|clock]] or [[Regulator overview|regulator]] used as reference voltage and common registers. * {{CodeSource | Linux kernel | drivers/iio/dac/stm32-dac.c | stm32-dac driver}} to handle the resources available for each DAC such as channel configuration or output buffer handling (power-down mode). ==References== <references />
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