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STMicroelectronics STM32 DFSDM ADC device driver
STM32 DFSDM ADC is a sigma delta analog-to-digital converter dedicated to
interface external sigma delta modulators to STM32 micro controllers.
It is mainly targeted for:
- Sigma delta modulators (motor control, metering...)
- PDM microphones (audio digital microphone)
It features up to 8 serial digital interfaces (SPI or Manchester) and
up to 4 filters on stm32h7 or 6 filters on stm32mp1.
Each child node match with a filter instance.
Contents of a STM32 DFSDM root node:
Required properties:
- compatible: Should be one of:
- reg: Offset and length of the DFSDM block register set.
- clocks: IP and serial interfaces clocking. Should be set according
to rcc clock ID and "clock-names".
- clock-names: Input clock name "dfsdm" must be defined,
"audio" is optional. If defined CLKOUT is based on the audio
clock, else "dfsdm" is used.
- #interrupt-cells = <1>;
- #address-cells = <1>;
- #size-cells = <0>;
Optional properties:
- spi-max-frequency: Requested only for SPI master mode.
SPI clock OUT frequency (Hz). This clock must be set according
to "clock" property. Frequency must be a multiple of the rcc
clock frequency. If not, SPI CLKOUT frequency will not be
- pinctrl-names: Set to "default".
- pinctrl-0: List of phandles pointing to pin configuration
nodes to set pins in mode of operation for dfsdm
on external pin.
Contents of a STM32 DFSDM child nodes:
Required properties:
- compatible: Must be:
"st,stm32-dfsdm-adc" for sigma delta ADCs
"st,stm32-dfsdm-dmic" for audio digital microphone.
- reg: Specifies the DFSDM filter instance used.
Valid values are from 0 to 3 on stm32h7, 0 to 5 on stm32mp1.
- interrupts: IRQ lines connected to each DFSDM filter instance.
- st,adc-channels: List of single-ended channels muxed for this ADC.
valid values:
"st,stm32h7-dfsdm" compatibility: 0 to 7.
- st,adc-channel-names: List of single-ended channel names.
- st,filter-order: SinC filter order from 0 to 5.
0: FastSinC
[1-5]: order 1 to 5.
For audio purpose it is recommended to use order 3 to 5.
- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers".
Required properties for "st,stm32-dfsdm-adc" compatibility:
- io-channels: From common IIO binding. Used to pipe external sigma delta
modulator or internal ADC output to DFSDM channel.
This is not required for "st,stm32-dfsdm-pdm" compatibility as
PDM microphone is binded in Audio DT node.
Required properties for "st,stm32-dfsdm-pdm" compatibility:
- #sound-dai-cells: Must be set to 0.
- dma: DMA controller phandle and DMA request line associated to the
filter instance (specified by the field "reg")
- dma-names: Must be "rx"
Optional properties:
- st,adc-channel-types: Single-ended channel input type.
- "SPI_R": SPI with data on rising edge (default)
- "SPI_F": SPI with data on falling edge
- "MANCH_R": manchester codec, rising edge = logic 0, falling edge = logic 1
- "MANCH_F": manchester codec, rising edge = logic 1, falling edge = logic 0
- st,adc-channel-clk-src: Conversion clock source.
- "CLKIN": external SPI clock (CLKIN x)
- "CLKOUT": internal SPI clock (CLKOUT) (default)
- "CLKOUT_F": internal SPI clock divided by 2 (falling edge).
- "CLKOUT_R": internal SPI clock divided by 2 (rising edge).
- st,adc-alt-channel: Must be defined if two sigma delta modulator are
connected on same SPI input.
If not set, channel n is connected to SPI input n.
If set, channel n is connected to SPI input n + 1.
- st,filter0-sync: Set to 1 to synchronize with DFSDM filter instance 0.
Used for multi microphones synchronization.
Example of a sigma delta adc connected on DFSDM SPI port 0
and a pdm microphone connected on DFSDM SPI port 1:
ads1202: simple_sd_adc@0 {
compatible = "ads1202";
#io-channel-cells = <1>;
dfsdm: dfsdm@40017000 {
compatible = "st,stm32h7-dfsdm";
reg = <0x40017000 0x400>;
clocks = <&rcc DFSDM1_CK>;
clock-names = "dfsdm";
#interrupt-cells = <1>;
#address-cells = <1>;
#size-cells = <0>;
dfsdm_adc0: filter@0 {
compatible = "st,stm32-dfsdm-adc";
#io-channel-cells = <1>;
reg = <0>;
interrupts = <110>;
st,adc-channels = <0>;
st,adc-channel-names = "sd_adc0";
st,adc-channel-types = "SPI_F";
st,adc-channel-clk-src = "CLKOUT";
io-channels = <&ads1202 0>;
st,filter-order = <3>;
dfsdm_pdm1: filter@1 {
compatible = "st,stm32-dfsdm-dmic";
reg = <1>;
interrupts = <111>;
dmas = <&dmamux1 102 0x400 0x00>;
dma-names = "rx";
st,adc-channels = <1>;
st,adc-channel-names = "dmic1";
st,adc-channel-types = "SPI_R";
st,adc-channel-clk-src = "CLKOUT";
st,filter-order = <5>;