STM32MP15 VREFBUF internal peripheral: Difference between revisions

Latest revision as of 16:18, 20 August 2024↑

Applicable for

1. Article purpose↑

The purpose of this article is to:

briefly introduce the VREFBUF peripheral and its main features,
indicate the peripheral instances assignment at boot time and their assignment at runtime (including whether instances can be allocated to secure contexts),
list the software frameworks and drivers managing the peripheral,
explain how to configure the peripheral.

2. Peripheral overview↑

The VREFBUF peripheral is an internal voltage regulator.

The VREFBUF is supplied via the VDDA pin. When enabled, it can provide a reference voltage in the range of: 1,5V, 1,8V, 2,048V or 2,5V.

The VREFBUF can be used to provide an analog voltage reference for:

ADC internal peripheral
DAC internal peripheral
External components through the dedicated VREF+ pin.

The VREFBUF can be left unused. In this case, an external voltage regulator can provide reference voltage to VREF+ pin.

Refer to the STM32MP15 reference manuals for the complete list of features, and to the software frameworks and drivers, introduced below, to see which features are implemented.

3. Peripheral usage↑

This chapter is applicable in the scope of the OpenSTLinux BSP running on the Arm^® Cortex^®-A processor(s), and the STM32CubeMPU Package running on the Arm^® Cortex^®-M processor.

3.1. Boot time assignment↑

3.1.1. On STM32MP15x lines ↑

The VREFBUF is not used at boot time.

3.2. Runtime assignment↑

3.2.1. On STM32MP15x lines ↑

Click on to expand or collapse the legend...

Domain	Peripheral	Runtime allocation				Comment
Domain	Peripheral	Instance	Cortex-A7 secure (OP-TEE)	Cortex-A7 non-secure (Linux)	Cortex-M4 (STM32Cube)	Comment
Analog	VREFBUF	VREFBUF		☐	☐	Assignment (single choice)

4. Software frameworks and drivers↑

Below are listed the software frameworks and drivers managing the VREFBUF peripheral for the embedded software components listed in the above tables.

Linux^®: regulator framework

Information

The VREFBUF is a system resource^[1] which needs to be also controlled by the resource manager^[1] in case its consumers (e.g. ADC, DAC or an external device connected to VREF+ pin) are spread across:

the Arm^® Cortex^®-A7 non-secure context
the Arm^® Cortex^®-M4 context

For this reason, the direct control of VREFBUF from the Arm^® Cortex^®-M4 is not recommended in STM32Cube by default.
It's recommended to implement it in STM32Cube only if all consumers and the VDDA supply pin are controlled in the Arm^® Cortex^®-M4 context.

5. How to assign and configure the peripheral↑

The peripheral assignment can be done via the STM32CubeMX graphical tool (and manually completed if needed).
This tool also helps to configure the peripheral:

partial device trees (pin control and clock tree) generation for the OpenSTLinux software components,
HAL initialization code generation for the STM32CubeMPU Package.

The configuration is applied by the firmware running in the context in which the peripheral is assigned.

For the Linux kernel configuration, please refer to device internal regulator. An example can be found also in ADC DT configuration examples
In case the control of VREFBUF consumers are spread across the various cores, see also Resource manager for coprocessing

6. References↑

↑ ^{Jump up to: 1.0} ^1.1 Resource manager for coprocessing, focus on system resources

[resource_manager-1] {Jump up to: 1.0} ^1.1 Resource manager for coprocessing, focus on system resources

[1]

@@ Line 1: / Line 1: @@
 <noinclude>{{ApplicableFor
 |MPUs list=STM32MP15x
-|MPUs checklist=STM32MP13x, STM32MP15x
+|MPUs checklist=STM32MP13x, STM32MP15x, STM32MP25x
 }}</noinclude>
 ==Article purpose==
-The purpose of this article is to
+The purpose of this article is to:
-* briefly introduce the VREFBUF  peripheral and its main features
+* briefly introduce the VREFBUF peripheral and its main features,
-* indicate the level of security supported by this hardware block
+* indicate the peripheral instances assignment at boot time and their assignment at runtime (including whether instances can be allocated to secure contexts),
-* explain how each instance can be allocated to the runtime contexts and linked to the corresponding software components
+* list the software frameworks and drivers managing the peripheral,
-* explain, when needed, how to configure the VREFBUF peripheral.
+* explain how to configure the peripheral.
 ==Peripheral overview==
-The '''VREFBUF''' peripheral is an internal voltage regulator.
+The '''VREFBUF ''' peripheral is an internal voltage regulator.
-===Features===
 The VREFBUF is supplied via the VDDA pin. When enabled, it can provide a reference voltage in the range of: 1,5V, 1,8V, 2,048V or 2,5V.
 The VREFBUF can be used to provide an analog voltage reference for:
-* ADC internal peripheral<ref name="adc_internal">[[ADC internal peripheral]]</ref>
+* [[ADC internal peripheral]]
-* DAC internal peripheral<ref name="dac_internal">[[DAC internal peripheral]]</ref>
+* [[DAC internal peripheral]]
 * External components through the dedicated VREF+ pin.
 The VREFBUF can be left unused. In this case, an external voltage regulator can provide reference voltage to VREF+ pin.
-Refer to the [[STM32MP15 resources#Reference manuals|STM32MP15 reference manuals]] for the complete list of features, and to the software components, introduced below, to know which features are really implemented.
+Refer to the [[STM32MP15 resources#Reference manuals|STM32MP15 reference manuals]] for the complete list of features, and to the software frameworks and drivers, introduced below, to see which features are implemented.
+==Peripheral usage==
+This chapter is applicable in the scope of the '''OpenSTLinux BSP''' running on the Arm<sup>&reg;</sup> Cortex<sup>&reg;</sup>-A processor(s), and the '''STM32CubeMPU Package''' running on the Arm<sup>&reg;</sup> Cortex<sup>&reg;</sup>-M processor.
+===Boot time assignment===
+====On {{MicroprocessorDevice | device=15}}====
+The VREFBUF is not used at boot time.
+===Runtime assignment===
+====On {{MicroprocessorDevice | device=15}}====
+{{#lst:STM32MP1_internal_peripherals_assignment_table_template|stm32mp15_runtime}}
+<section begin=stm32mp15_runtime />
+ | rowspan="1" | Analog
+ | rowspan="1" | [[STM32MP15 VREFBUF internal peripheral|VREFBUF]]
+ | VREFBUF
+ |
+ | <span title="assignable peripheral" style="font-size:21px">☐</span>
+ | <span title="assignable peripheral" style="font-size:21px">☐</span>
+ | Assignment (single choice)
+ |-
+<section end=stm32mp15_runtime />
+|}
-===Security support===
+==Software frameworks and drivers==
-The VREFBUF is a '''non-secure''' peripheral.
+Below are listed the software frameworks and drivers managing the VREFBUF peripheral for the embedded software components listed in the above tables.
-==Peripheral usage and associated software==
+* '''Linux<sup>&reg;</sup>''': [[Regulator overview|regulator framework]]
-===Boot time===
-The VREFBUF is usually not used at boot time. But it may be needed by the SSBL (see [[Boot chain overview]]), to supply the internal ADC<ref name="adc_internal"/> for example.
-===Runtime===
+{{Info|The VREFBUF is a system resource<ref name="resource manager">[[Resource_manager_for_coprocessing#The_system_resources|Resource manager for coprocessing]], focus on system resources</ref> which needs to be also controlled by the resource manager<ref name="resource manager"/> in case its consumers (e.g. [[ADC internal peripheral|ADC]], [[ADC internal peripheral|DAC]] or an external device connected to VREF+ pin) are spread across:
-====Overview====
-The VREFBUF can be allocated to the Arm<sup>&reg;</sup> Cortex<sup>&reg;</sup>-A7 non-secure to be used under Linux<sup>&reg;</sup> with regulator framework<ref name="regulator">[[Regulator overview]], Linux<sup>&reg;</sup> regulator framework overview</ref>.
-{{Info|The VREFBUF is a system resource<ref name="resource manager">[[Resource_manager_for_coprocessing#The_system_resources|Resource manager for coprocessing]], focus on system resources</ref> which needs to be also controlled by the resource manager<ref name="resource manager"/> in case its consumers (e.g. ADC<ref name="adc_internal"/>, DAC<ref name="dac_internal"/> or an external device connected to VREF+ pin) are spread across:
 * the Arm<sup>&reg;</sup> Cortex<sup>&reg;</sup>-A7 non-secure context
 * the Arm<sup>&reg;</sup> Cortex<sup>&reg;</sup>-M4 context
-For this reason, the direct control of VREFBUF from the Arm<sup>&reg;</sup> Cortex<sup>&reg;</sup>-M4 is not recommended in STM32Cube<ref name="STM32Cube">[[STM32CubeMP1 architecture]]</ref> by default.<br/>
+For this reason, the direct control of VREFBUF from the Arm<sup>&reg;</sup> Cortex<sup>&reg;</sup>-M4 is not recommended in [[STM32CubeMP15 Package architecture|STM32Cube]] by default.<br/>
 It's recommended to implement it in STM32Cube '''only if''' all consumers and the VDDA supply pin are controlled in the Arm<sup>&reg;</sup> Cortex<sup>&reg;</sup>-M4 context.
 }}
-The [[#Peripheral assignment|Peripheral assignment]] chapter describes which peripheral instance can be assigned to which context.
+==How to assign and configure the peripheral==
+The peripheral assignment can be done via the [[STM32CubeMX]] graphical tool (and manually completed if needed).<br />
-====Software frameworks====
+This tool also helps to configure the peripheral:
-{{:STM32MP15_internal_peripherals_software_table_template}}
+* partial device trees (pin control and clock tree) generation for the OpenSTLinux software components,
- | Analog
+* HAL initialization code generation for the STM32CubeMPU Package.
- | [[STM32MP15 VREFBUF internal peripheral|VREFBUF]]
+The configuration is applied by the firmware running in the context in which the peripheral is assigned.
- |
- | Linux [[Regulator overview|regulator]] framework
- |
- |
- |-
- |}
-====Peripheral configuration====
-The configuration is applied by the firmware running in the context to which the peripheral is assigned. The configuration by itself can be performed via the [[STM32CubeMX]] tool for all internal peripherals. It can then be manually completed (especially for external peripherals) according to the information given in the corresponding software framework article.
-* For the Linux kernel configuration, please refer to [[Regulator_overview#Microcontroller_device_internal_regulator|device internal regulator]]. An example can be found also in [[ADC_device_tree_configuration#DT_configuration_example|ADC DT configuration example]]
+* For the Linux kernel configuration, please refer to [[Regulator_overview#Microprocessor_device_internal_regulator|device internal regulator]]. An example can be found also in [[ADC_device_tree_configuration#DT_configuration_examples|ADC DT configuration examples]]
 * In case the control of VREFBUF consumers are spread across the various cores, see also [[Resource manager for coprocessing]]
-====Peripheral assignment====
-{{:STM32MP15_internal_peripherals_assignment_table_template}}
-<onlyinclude>
- | rowspan="1" | Analog
- | rowspan="1" | [[STM32MP15 VREFBUF internal peripheral|VREFBUF]]
- | VREFBUF
- |
- | <span title="assignable peripheral" style="font-size:21px">☐</span>
- |
- | Assignment (single choice)
- |-
-</onlyinclude>
- |}
 ==References==
 <references/>
 <noinclude>
 [[Category:Analog peripherals|VREFBUF internal peripheral STM32MP15]]
+{{ArticleBasedOnModel| Internal peripheral article model}}
 {{PublicationRequestId | 8312 | 2018-08-07 | AlainF}}
-{{ArticleBasedOnModel| Internal peripheral article model}}
-{{ReviewsComments|JCT 1840: alignment needed with the last version of the model<br>
-[[Category:ToBeAlignedWithModel]]
-}}
 </noinclude>