130 lines
4 KiB
Plaintext
130 lines
4 KiB
Plaintext
Qualcomm's SPMI PMIC voltage ADC
|
|
|
|
SPMI PMIC voltage ADC (VADC) provides interface to clients to read
|
|
voltage. The VADC is a 15-bit sigma-delta ADC.
|
|
|
|
VADC node:
|
|
|
|
- compatible:
|
|
Usage: required
|
|
Value type: <string>
|
|
Definition: Should contain "qcom,spmi-vadc".
|
|
|
|
- reg:
|
|
Usage: required
|
|
Value type: <prop-encoded-array>
|
|
Definition: VADC base address and length in the SPMI PMIC register map.
|
|
|
|
- #address-cells:
|
|
Usage: required
|
|
Value type: <u32>
|
|
Definition: Must be one. Child node 'reg' property should define ADC
|
|
channel number.
|
|
|
|
- #size-cells:
|
|
Usage: required
|
|
Value type: <u32>
|
|
Definition: Must be zero.
|
|
|
|
- #io-channel-cells:
|
|
Usage: required
|
|
Value type: <u32>
|
|
Definition: Must be one. For details about IIO bindings see:
|
|
Documentation/devicetree/bindings/iio/iio-bindings.txt
|
|
|
|
- interrupts:
|
|
Usage: optional
|
|
Value type: <prop-encoded-array>
|
|
Definition: End of conversion interrupt.
|
|
|
|
Channel node properties:
|
|
|
|
- reg:
|
|
Usage: required
|
|
Value type: <u32>
|
|
Definition: ADC channel number.
|
|
See include/dt-bindings/iio/qcom,spmi-vadc.h
|
|
|
|
- qcom,decimation:
|
|
Usage: optional
|
|
Value type: <u32>
|
|
Definition: This parameter is used to decrease ADC sampling rate.
|
|
Quicker measurements can be made by reducing decimation ratio.
|
|
Valid values are 512, 1024, 2048, 4096.
|
|
If property is not found, default value of 512 will be used.
|
|
|
|
- qcom,pre-scaling:
|
|
Usage: optional
|
|
Value type: <u32 array>
|
|
Definition: Used for scaling the channel input signal before the signal is
|
|
fed to VADC. The configuration for this node is to know the
|
|
pre-determined ratio and use it for post scaling. Select one from
|
|
the following options.
|
|
<1 1>, <1 3>, <1 4>, <1 6>, <1 20>, <1 8>, <10 81>, <1 10>
|
|
If property is not found default value depending on chip will be used.
|
|
|
|
- qcom,ratiometric:
|
|
Usage: optional
|
|
Value type: <empty>
|
|
Definition: Channel calibration type. If this property is specified
|
|
VADC will use the VDD reference (1.8V) and GND for channel
|
|
calibration. If property is not found, channel will be
|
|
calibrated with 0.625V and 1.25V reference channels, also
|
|
known as absolute calibration.
|
|
|
|
- qcom,hw-settle-time:
|
|
Usage: optional
|
|
Value type: <u32>
|
|
Definition: Time between AMUX getting configured and the ADC starting
|
|
conversion. Delay = 100us * (value) for value < 11, and
|
|
2ms * (value - 10) otherwise.
|
|
Valid values are: 0, 100, 200, 300, 400, 500, 600, 700, 800,
|
|
900 us and 1, 2, 4, 6, 8, 10 ms
|
|
If property is not found, channel will use 0us.
|
|
|
|
- qcom,avg-samples:
|
|
Usage: optional
|
|
Value type: <u32>
|
|
Definition: Number of samples to be used for measurement.
|
|
Averaging provides the option to obtain a single measurement
|
|
from the ADC that is an average of multiple samples. The value
|
|
selected is 2^(value).
|
|
Valid values are: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512
|
|
If property is not found, 1 sample will be used.
|
|
|
|
NOTE:
|
|
|
|
Following channels, also known as reference point channels, are used for
|
|
result calibration and their channel configuration nodes should be defined:
|
|
VADC_REF_625MV and/or VADC_SPARE1(based on PMIC version) VADC_REF_1250MV,
|
|
VADC_GND_REF and VADC_VDD_VADC.
|
|
|
|
Example:
|
|
|
|
/* VADC node */
|
|
pmic_vadc: vadc@3100 {
|
|
compatible = "qcom,spmi-vadc";
|
|
reg = <0x3100 0x100>;
|
|
interrupts = <0x0 0x31 0x0 IRQ_TYPE_EDGE_RISING>;
|
|
#address-cells = <1>;
|
|
#size-cells = <0>;
|
|
#io-channel-cells = <1>;
|
|
io-channel-ranges;
|
|
|
|
/* Channel node */
|
|
usb_id_nopull {
|
|
reg = <VADC_LR_MUX10_USB_ID>;
|
|
qcom,decimation = <512>;
|
|
qcom,ratiometric;
|
|
qcom,hw-settle-time = <200>;
|
|
qcom,avg-samples = <1>;
|
|
qcom,pre-scaling = <1 3>;
|
|
};
|
|
};
|
|
|
|
/* IIO client node */
|
|
usb {
|
|
io-channels = <&pmic_vadc VADC_LR_MUX10_USB_ID>;
|
|
io-channel-names = "vadc";
|
|
};
|