1. Article purpose[edit | edit source]
The purpose of this article is to:
- briefly introduce the DAC 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[edit | edit source]
The DAC peripheral is a voltage output digital-to-analog converter:
- It may be configured in 8- or 12-bit mode (data could be left- or right-aligned)
- It has two output channels, each with its own converter
- The dual DAC channel mode could be done independently or simultaneously
- It has built-in noise and triangle waveform generator and supports triggers for conversions, using: TIM[1], LPTIM[2] or EXTI[3]
- The DAC output buffer allows a high drive output current
- It can operate under Normal mode or low-power Sample and Hold mode (uses LSI clock, from RCC[4]).
- It may be used in conjunction with the DMA[5] controller (with underrun error detection)
- The common reference voltage, can be provided by either VREFBUF[6] or any other external regulator[7] wired 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[edit | edit source]
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[edit | edit source]
The DAC peripheral is not used at boot time.
3.2. Runtime assignment[edit | edit source]
3.2.1. On STM32MP15x lines 
[edit | edit source]
Click on 
to expand or collapse the legend...
Check boxes illustrate the possible peripheral allocations supported by STM32 MPU Embedded Software:
- ⬚ means that the peripheral can be assigned to the given runtime context, but this configuration is not supported in STM32 MPU Embedded Software distribution.
- ☐ means that the peripheral can be assigned to the given runtime context.
- ☑ means that the peripheral is assigned by default to the given runtime context and that the peripheral is mandatory for the STM32 MPU Embedded Software distribution.
- ✓ is used for system peripherals that cannot be unchecked because they are hardware connected in the device.
Refer to How to assign an internal peripheral to an execution context for more information on how to assign peripherals manually or via STM32CubeMX.
The present chapter describes STMicroelectronics recommendations or choice of implementation. Additional possiblities might be described in STM32MP15 reference manuals.
| Domain | Peripheral | Runtime allocation | Comment
| |||
|---|---|---|---|---|---|---|
| Instance | Cortex-A7 secure (OP-TEE) |
Cortex-A7 non-secure (Linux) |
Cortex-M4 (STM32Cube) | |||
| Analog | DAC | DAC | ☐ | ☐ | Assignment (single choice) | |
4. Software frameworks and drivers[edit | edit source]
Below are listed the software frameworks and drivers managing the DAC peripheral for the embedded software components listed in the above tables.
- Linux®: IIO framework
- STM32Cube: HAL DAC driver
5. How to assign and configure the peripheral[edit | edit source]
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 DAC device tree configuration and DAC Linux driver articles.
6. References[edit | edit source]
Arm® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere. 
Arm® is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.