Category: Getting Started and Peripheral Coding

What is PWM? PWM or Pulse Width Modulation, is a type of digital electrical signal which is periodic in nature, with a rectangular waveform. There are certain terms associated with PWM which we need to understand before we move ahead. Here’s a graphical representation of a PWM signal- ·       ‘Period’ = Tp , is the time it takes to repeat the same waveform ·       ‘Duty cycle’ is the time for which the signal is a logic 1 by the total time period. Ton is the time for which the pulse is high Hence, Duty cycle % = (Ton/ Tp) X 100 ·       ‘Frequency’ = F is the number of times the waveform repeats in a second. So, F = 1/Tp. Applications of PWM signals PWM signals have an extremely wide range of applications, here are a few of them- ·       Variable voltage generator– if you vary the duty cycle of a PWM signal and apply it to certain electrical components, the components act as if they are receiving analog signals. This is because the response time of the components is finite. So, components like LEDs, buzzers, brushed DC motors etc. can be controlled by PWM signals. Meaning, you could control speed of a motor, brightness of an LED or amplitude of a buzzer and so on. The voltage that they receive has a linear relationship with the duty cycle. So, if logic 1 is 5 Volts 0% duty cycle – 0V 25% duty cycle – 1.25 V 50% duty cycle – 2.5 V 75% duty cycle – 3.75V 100% duty cycle – 5V ·       As a control signal – Some electrical devices/components analyze PWM signals that they are receiving to give a corresponding output. So, changes in the duty cycle are reflected in the output. These include Servo motors, electronic speed controllers (ESCs) and many more. Here, the devices respond only to specific PWM duty cycles and frequencies If you take the example of servo motors, they can only be operated at 50Hz signal with a duty cycle of 2.5 % to 12% . Anything beyond that doesn’t result in the movement of the servo. (The frequency and duty cycles vary from among different servos, this is a very common value which most 180-degree servos respond to) Similarly, ESCs respond to a PWM signal with ON time of 1ms for minimum throttle and 2ms for maximum throttle with PWM frequency of 50 Hz. Some devices such as HCSR04 ultrasonic sensors give an output as a PWM signal in which the pulse width corresponds to the time it took for the ultrasonic wave to be received. How is PWM signal Generated on STM32?? Timer peripheral STM32 blue pill has 15 pins which can generate a PWM signal, with other models having even more pins for PWM generation. In this section, we will try to understand how PWM signals are generated by STM32 Every microcontroller has a built-in circuit which can measure the passing of time. These are called Timers. What timers essentially do is count up to a certain number and upon reaching that number, they change the value of a certain register to indicate that the timer has counted up to that number. Now, the time it takes to increment this count by 1 is determined by the timer’s clock frequency. So, if the frequency of a timer is 1KHz, its time period will be 1 Millisecond. Hence, if we count up to 10, we have measured the passing of 10 Milliseconds. This is how, by simply incrementing a number, timers can measure the time that has passed since the timer began counting. (This is how the HAL_Delay() function generates delays) The maximum count a timer can make is determined by its register size. So, an 8 bit timer can count up to 28 = 256, 10-bit timer –210 = 1024 16-bit timer –216 = 65536 32-bit timer –232 = 4294967296 So, a 1 bit increase in timer size equals to double the count Timers are extremely necessary for the functioning of a microcontroller as a lot of events in programs are time based, which you may not even realize. Timer Peripheral modes and features Coming to STM32 Blue pill, it has 4 timers of 16-bit size. To perform these functions, they need to be in specific modes. Here are all the modes in which timers can operate in STM32- 1.    Input capture mode– In this mode, a pin on the board is set as input on which a PWM signal is sent by some device and we measure the frequency and duty cycle of that signal. This can be used to interface with devices such as HCSR04 ultrasonic sensors, which send a PWM signal as input to the microcontroller, where different parameters of PWM signals can be used to determine the distance which the sensor is trying to measure. 2.    Output compare mode– In this mode, the timer is used as a counter and the count is compared to a register which contains a pre-programmed value, when they are equal, a software interrupt is generated and using this, a given pin is switched high or low. This mode comes in very handy when you are making a project which requires you to use multiple peripherals and at the same time generate a rectangular waveform of a given frequency and duty cycle, as it is interrupt based. 3.    One pulse mode– In this mode, a pulse can be generated based upon a trigger from an input pin on the board , the pulse generation takes place after a certain delay from when the input trigger pulse was detected. This can be considered as a combination of mode 1&2 (IC &OC) 4.    PWM generation mode– In this mode, we can generate a PWM signal on a given pin by fixing a frequency and a duty cycle. This is the mode we will be using to generate PWM signals through the main loop. The difference of this mode to mode 2 (Output compare

What is STM32 ? STM32 is a family of 32-bit Microcontrollers and development boards manufactured by ST Microelectronics which offer very high performance for a relatively low price. All STM32 microcontrollers are based on ARM Cortex-M processor which make them much better in terms of computing power than most of the common microcontrollers/microcontroller development boards which are available in the market. These microcontrollers also have been provided with software support by ST for developers for free. If you have experience with microcontrollers like Arduino, this is a great step forward in understanding microcontrollers in depth. The STM32 framework allows you to control all peripherals and allows you to tweak them as per your wish, whereas in Arduino IDE, when you program in C++, it comes with in-built functions and libraries which don’t allow you to understand the backend working behind everything. This is very crucial, as it allows you to use the microcontroller to its full potential. STM32 FAMILY The STM32 family of microcontrollers is vast and expansive, offering a variety of options for the consumer to choose from. The family of microcontrollers is broadly classified into 4 categories- High performance ST offers a series of microcontrollers which have the fastest code execution time, high speed data transfer and relatively higher flash memory. Along with this, the feature the most advance peripherals that ST offers. This makes these controllers very useful for real-time applications such as running an RTOS. STM32H7x The H7 series controllers are based on the ARM Cortex M7 offering very high speeds of upto 550Mhz. The microcontroller series comes in two variants, single core and dual core. Dual core H7 series controllers come with an ARM Cortex M4 core as well as an ARM Cortex M7 core which allows for processing work distribution, very useful for applications requiring many peripherals where response time is critical. The dual Core variants also come with an inbuilt SMPS as well. The single core series comes with an ARM Cortex M7 core with clock speed between 220-550Mhz, depending upon the variant. STM32F7x The F7 series controllers are based on the ARM Cortex M7, Thanks to an L1 (level 1) cache, the series delivers the maximum possible theoretical performance of the Cortex-M7 core. Cache memory temporarily stores instructions frequently accessed by the processor STM32F4x – The F4 series is based on the ARM Cortex M4. These controllers have less processing power then H7 and F7 series but still come with advanced peripherals and high flash memory. A very useful line of microcontrollers which offer a wide variety of features and come at a relatively lower cost than that of an F7/H7 controllers. The F4 series is broadly divided into 3 segments- 1.F4 Advance line- Offers up to 180Mhz of clock speed and a maximum of 2 Mb of dual bank flash memory, with advanced peripherals, consisting of communication buses such as QSPI. 2.F4 foundation line- Offer lower flash memory (between 512Kb-1Mb) , with few controllers offering advance peripherals and features such as camera interface and Ethernet MAC. 3.F4 Access line- This line of F4 controllers consists of entry level controller which can be termed ‘High Performance’. These controllers come with lower clock speeds, lower RAM but feature very good power efficiency, while also not compromising on peripherals. Wireless The main focus of the STM32Wx microcontroller family is wireless connectivity. They cover sub-GHz as well as 2.4Ghz frequency range operation The STM32 wireless MCUs are further divided into 2 categories– STM32WB These MCUs have a dual core processor unit, Cortex M4 & Cortex M0+, which allows for processing distribution, making it a great candidate for real-time processing and execution. The MCU series is based on STM32L4 architecture, which offers dynamic voltage scaling, reducing the power consumption of the device. They also support BLE 5.3, Open Thread and Zigbee protocols, making them a great choice for IOT applications, providing a lot of functionality onboard the chip itself. STM32WL These MCUs also come with a dual core processor unit like the STM32WB series, and some variants also come with a single ARM Cortex M4 as their processing unit. The key highlight of this series of microcontrollers is that not only do they work as a general purpose microcontroller, but also come with an integrated sub GHz radio supporting LoRa WAN which makes it a great choice for smart home applications, utilities, logistics, Industrial IOT etc.   Ultra-Low Power – STM32 ultra-low-power microcontrollers offer designers of energy-efficient embedded systems and applications a balance between performance, power, security and cost effectiveness. The portfolio includes the STM8L (8-bit proprietary core), the STM32L4 (Arm® Cortex®-M4), the STM32L0 (Arm® Cortex®-M0+) and the STM32L1 (Arm® Cortex®-M3). The STM32L5 MCU (Arm® Cortex®-M33) with its enhancedsecurity features is the latest addition to this rich portfolio. The new STM32U5 series combines the latest and most efficient Arm Cortex-M33 core with an innovative 40 nm platform that reduces energy consumption to the bone, while increasing performance. The series also adds the state-of-the-art features which are required in today’s applications,including advanced cyber security with hardware-based protection, and graphics accelerators for rich graphical user interfaces. The STM32L5 series enhanced security features leverage Arm® Cortex®-M33 and its TrustZone® for Armv8-M. Thanks to this new core and a new ST ART Accelerator™ (also supporting external memory), the STM32L5 reaches an 443 CoreMark. The STM32L4 series offers the excellence of ST’s ultra-low power platform with an additional performance dimension by providing 100 DMIPS with DSP instructions and Floating-Point Unit (FPU), more memory (up to 1 Mbyte of Flash memory) and innovative features. The STM32L4+ series extends STM32L4 technology by offering higher performance (120 MHz/409 CoreMark executing from internal Flash memory), larger embedded memories (up to 2 Mbytes of Flash memory and 640 Kbytes of SRAM), and rendering advanced graphics without compromising ultra-low-power consumption. The STM32L0 series offers a genuine energy-saving solution for entry-level applications. Available in tiny packages down to 14 pins and with a wide range of Flash memory densities from 8 to 192 Kbytes, the STM32L0 features ultra-low power consumption in a competitive portfolio. Mainstream– The mainstream microcontrollers are more general-purpose boards

In the last post, we have gotten to know about the features of ADC Peripheral that we have in STM32 MCU. Now in this blog with the series of bare Metal Programming for Blue Pill, we will understand different register bytes and bits of ADC Peripheral to be used for using it in different features, configurations, and modes as we get to know about in the Previous Post. In this blog, we will be going through how to use  ADC Peripheral for converting a Single Channel of ADC (only one ADC pin) and see its bare metal code. Single  Channel Conversion  Mode: Only one ADC pin is used, this mode is like when we have say connected only one analog sensor to one of the ADC pins of MCU  like the Potentiometer is connected at PA0 pin. ADC Registers In depth for: Let\’s get into an in-depth understanding of which registers and their bits are used for configuring the ADC peripheral of Blue Pill in Single Channel Configuration. We will focus on bits and will give an explanation of why those bits are used for the 1.   ADC_SR(ADC status Register) –>This register tells the status of ADC channel  Conversion, as it name says. STM32F103 ADC Status Register: 11.12.1 Bit 1[EOC ]: This bit is set by hardware when a single channel of any group (Regular or Injected) is converted successfully. So this bit is used for monitoring when the ADC conversion is completed by using it inside the while loop if interrupts are disabled. 0: ADC Channel Conversion is not completed 1: ADC Channel Conversion is completed When hardware set this bit, we can clear this bit from the firmware end by setting the bit to 0 or by reading ADC_DR(ADC Data Register) Bit 4[STRT]: This bit is set by hardware when regular channel conversion has begun. So when we start the Regular Channel Conversion, we will use this bit inside the while loop to check that whether Regular Channel conversion has started or not. 0: No regular Channel Conversion has started 1: Regular Channel Conversion has started When hardware sets this bit, we can clear this bit from the firmware end by setting the bit to 0. Even if we don\’t clear this bit it will cause no effect during ADC Conversion. But its good practise to clear all bits of Status Register before starting the new conversion 2.            ADC_DR(ADC Data Register) –> This register stores the converted digital data at a 12-bit resolution of the converted ADC channel. STM32F103 ADC Data Register 11.12.14 Bit 15:0 [DATA 15:0]: The ADC_DR is divided into two 16 bits groups. The first 16 bits from 0-15 contain the Converted value of the configured ADC Regular Channel. As our ADC is of 12-bit resolution, so this is left aligned or right aligned to 4 bits so as to get the 12 ADC converted data . Left Aligned or Right alignment of ADC Data Depends on ALIGN bit of ADC_CR2 So we will have following code and algorithm for ADC_SR & ADC_DR register:while(!(ADC1->SR & ADC_SR_STRT)) while(!(ADC1->SR & ADC_SR_EOC)); // wait till a group channel converstion has completed adc_data = ADC1->DR; //clear the EOC bit by reading DR register ADC1->SR &= ~ADC_SR_STRT;      3.      ADC_CR1(ADC Configuration register 1) –> This register is used for the  Configuration of ADC peripheral for Analog Watchdog Discontinuous Mode Interrupt Enable/disable Dual Mode configuration Scan Mode  As we are not using any of these features, so all the bits for these registers will be set to zero, and to know about these features and their bit functions, u can navigate to corresponding blogs for those. STM32F103 ADC Configuration Register 1. 11.12.2 Bits 19:16 [DUALMODE 3:0]:  These bits are used to configure the type of operating mode. In the blue pill, we have two ADC peripherals: ADC1 & ADC2. We can use these  2 ADC peripherals simultaneously by configuring the respective ADC in different modes or in independent modes. We are going to use these ADC in independent mode as will be using only ADC1 peripheral, so DUALMODE[3:0] will be set to 0. Bit 8[SCAN]: This bit is used to enable/disable the SCAN Mode feature in the ADC peripheral of BLUEPILL. Scan Mode is used when we convert more than 1 channel to scan all the configured channels in a Regular Group. As we are using only a single channel, means only one ADC pin is used so SCAN mode is not used and this bit will be set to 0. 0: Scan Mode disabled. 1:Scan Mode Enabled. So we will have following code and algorith for ADC_CR1 register:ADC1->CR1 &= ~(ADC_CR1_SCAN); // SCAN DISABLED, if using scan mode then dma must be enabled ADC1->CR1 &= ~(ADC_CR1_JDISCEN | ADC_CR1_DISCEN); // Discontinous mode disabled for both injected and regular groups ADC1->CR1 &= ~(ADC_CR1_DISCNUM_2 | ADC_CR1_DISCNUM_1 | ADC_CR1_DISCNUM_2 ); // no channels are configured in discontinous way. // if discontinous mode is enabled then number of //conversions to be done by discontinous mode has to be configured // DISNUM bits ADC1->CR1 &= ~(ADC_CR1_DUALMOD_0 | ADC_CR1_DUALMOD_1 | ADC_CR1_DUALMOD_2); // INDEPENDENT MODE SELECTED ADC1->CR1 &= ~(ADC_CR1_AWDEN | ADC_CR1_JAWDEN); // Analog watchdog disabled for both groups: regular and ibnjected 4. ADC_CR2(ADC Configuration Register 2) –> This register is used for the configuration of  ADC Peripheral for:  ADC Conversion enables/disabled for regular and injected groups and ADC peripheral enable/disable. Trigger source configuration for regular and injected groups. ADC Data Alignment, DMA, Continous, temperature sensor setting. STM32F103 ADC Configuration Register 2 11.12.3 Bit 0 [ADON]: ADC Peripheral On/OFF. This bit will be set to 1 to enable the ADC peripheral.  All channel configurations and ADC Peripheral configurations have to be made before setting this bit to 1. 0: Disable ADC Peripheral 1: Enable ADC Peripheral Bit 1 [CONT]: This bit configures between Single Conversion mode and Continous Conversion mode. Continuous Conversion mode is selected when we have more than 1 ADC channel to be converted. As in this blog, we have

Home Category Child Category Introduction Imagine that we are building a robot or an interactive art piece. We might be interested in measuring temperature, distance to the nearest object, force, and acceleration, sound pressure level, brightness, or any other physical characteristics. The first step is to convert all these physical quantities into a voltage using a transducer. The world is analog in nature, so every quantity that we need to measure is measured by the transducer in an analog output. But our Computers, MCU, Processors are digital in nature, that is they can Understand only ‘1’ and ‘0’. Thus we need an interface that can convert analog values of the world into digital values so as to process them. Thus here comes the ADC(Analog to Digital converter) “Analog Signals need to be processed correctly before they can be converted into digital form. This processinbg of Analog Signal is done by Signal Conditioning circuits” Important Terms in ADC Resolution of ADC: As said, ADC transforms an analog voltage to a binary number(series of 1’s &0’s) which is then represented as a Digital Number over our screens. The Number of Binary digits (1 &0) that represents the Digital Number determines the ADC Resolution ADC Introduction in STM32 Like every modern family of MCU, STM32 too has inbuilt ADC. Now if we open the datasheet of STM32F103 Bluepill and Navigate to its ADC Section. Now let’s break down this ADC Introduction part to understand the ADC Peripheral in STM32 MCU Successive Approximation: Type of ADC which is used in STM32 MCU.Which is made using OPAMPS, Resistors, Digital & Analog Electronic Circuit. So depending upon the type of circuit their are different types of ADC. 1) Successive Approximation 2) Sigma Delta 3) Voltage to frequency 4)Dual Slope ADC Analog Sensors & Electronics are huge topic, so wont be able to cover everything & would be focusing on STM32 MCU ADC Peripheral Click Here12 Bit ADC : Resolution of the ADC Peripheral in STM32 MCUThis is Resolution of the ADC Peripheral in STM32 MCU.Means Decoded ADC value which we will get will be ranging from [0-4095] = 2^12Click Here18 Multiplexed Channels: Blue Pill we have 18 ADC pinsBasically channels means from which Analog Values of the External world/Transducer will be fed to the MCU. Out of the 18 Pins Blue Pill has 16 external and 2 internal sources. This means that in 1) 16 pins [ADC0-15], we can fed analog values from the external world, like interfacing some analog sensors 2) 2 pins[ADC16:17] have the internal analog sources (Internal temperature Sensor & Internal Reference Voltage) : There is one inbuilt Temperature sensor inside the MCU which Outputs the data in analog value & send it to ADC_Channel 16.Click Here Previous Next So that is for the basic introduction of the ADC peripheral of STM32F103, now let\’s dive into more in-depth to know about the features of ADC peripheral in STM32 MCU. ADC Features in STM32 MCU Regular and Injected groups In STM32 MCU ADC peripheral their is a feature of Regular and Injected Group, we can configure the ADC Channels to be either in Regular Group or Injected Group. Regular Group: ADC Channels which are configured in regular group are converted regularly( when ADC peripheral is started by setting ADC_CR2:ADON bit), just like basic ADC conversion of channels one by one Injected Group: Now Channels which are configured in injected group works on same principal of Regular Group but this group have higher priorty then Regular group. As it names says injected, this group will interrupt the Regular group Conversion Click Here Types of Conversion Modes in STM32 ADCTheir are 4 types of Channel Conversion Modes in STM32. 1) Single Conversion Mode 2) Continuous Conversion Mode 3) Scan Mode 4) Discontinuous ModeClick HereSingle Conversion Mode: As it name says \”Single Conversion\” so when ADC peripheral is configured to be in Single Conversion Mode , only one time conversion of configured ADC channels is done when ADC peripheral is triggered.Click HereContinous Conversion Mode:As it name says \”Continuous Conversion\”, so this is vice versa of single conversion. All the configured ADC channels are continuously converted once the ADC Peripheral is triggered by Software or by external event and converted data is continuously stored in ADC_DRClick HereScan Mode:This is 3rd type of Mode, as its name says\”Scan\”. So when configured in this mode, ADC works like a \”SCAN\”, it is used to scan a regular or injected group channel. In short, we can say if we are using more than 1 ADC channel & doing conversion of all configured ADC channels then we will be using Scan Mode. After the first channel conversion, it will go to the next configured channel for its conversion till the last channel configured Click HereDiscontinous Mode:This is 4th type of mode, in this mode we can convert configured channels of regular and injected group in short sequences of n conversion (n

first View What is a Processor Processor is programmable electronic circuitry that performs operations according to the instructions stored in memory. The processor as of itself does not have the memory and I/O devices. The processor reads the instructions stored in the memory, interprets it, and stores the output in memory or signals the I/Os. Processor Consists of the Processor core which contains circuitry for instruction fetching, decoding, and execution, register banks, and control units. According to the architecture design of the processor, the different processors have different components. For example, ARM cortex-M4 processors have NVIC, MPU, Floating point units, optional debug subsystems. This allows the microcontroller vendors to design differently. A block diagram of the microcontroller. Fig 1.2 – A microcontroller contains Many different blocks How does Processor control the world? Processors become an integral part of our life. We come across many devices which have processors embedded in them. For example: The smartphone on which I am writing this article has ARM cortex-A55 and cortex-A75 as processor,   The Famous Tesla motors FSD Self-driving computer has many ARM processors. To give the idea of how processors are running the world look at these two examples. Upto 2019, Arm partners have shipped more than 160 billion Arm-based chips. Due to the shortage of semiconductor chips(processors) many car manufacturing companies had to reduce the number of cars manufactured. ARM Processor ARM Processor ARM processors are designed by ARM Ltd., ARM does not manufacture processors or sell the chips directly. Instead ARM licenses these designs to other semiconductor companies so that they can make their processor, microcontroller, SOCs as ARM processors are configurable. In the Cortex processor range, the processors are divided into three profiles: 1) The A Profile is designed to handle complex applications such as high-end embedded OSs. 2) The R profile processors are targeted primarily at the high end of the real-time market. These are applications, such as hard drive controllers, automotive systems, etc. 3) The M profile processors target smaller-scale applications such as microcontrollers and mixed-signal design. ARM CortexA1) The A Profile is designed to handle complex applications such as high-end embedded OSs.Click HereARM Cortex RThe R profile processors are targeted primarily at the high end of the real-time market. These are applications, such as hard drive controllers, automotive systems, etc.Click HereARM Cortex MThe M profile processors target smaller-scale applications such as microcontrollers and mixed-signal design.Click Here Previous Next ARM develops new processors, new instructions, and architectural features are added from time to time, as a result, there are different versions of the architecture. For example: ARM7TDMI is based on the architecture version ARMv4T. ARMv5TE architecture was introduced with the ARM9E processor families. With the ARM11 Processor family, the architecture was extended to ARMv6 with memory system features and SIMD instructions included.  Cortex family processors are based on ARMv7 and ARMv6. The cortex-M3 and cortex-M4 processors are based on ARMv7-M architecture. The architecture evolution of the ARM can be seen in the following (Fig 1.4). All the cortex-M processors support Thumb-2 technology(16-bit and 32-bit instructions), with no need to switch the processor between Thumb state and ARM state. Keil MDK-ARMIAR systems(Embedded workbench for ARM Cortex-M) GCC_based IDEs Previous Next For Programming and debugging ARM Processor based MCU’s, we will be using Microcontrollers of different vendors like: STMicroelectronics and NXP Semiconductors. We will be using STM32 Family of STMicroelectronics and S32 Family of NXP Semiconductors. Both of these are based on ARM Processor and have rich set of features and specifications which are ideal for learning embedded systems. Now both the companies provide their own IDE’s for  : STM32CubeIDE and S32 Design IDE for respective family of MCU mentioned above. Or we can also use the Above-mentioned IDE’s which are general IDE’s can be used to program any ARM processor based MCU. But recomended one is to use Vendor specific IDE as it has many extra featutes for programming. CMSIS The Common Microcontroller Software Interface Standard(CMSIS) was developed by ARM to allow microcontroller and software vendors to use a consistent software infrastructure to develop software solutions for cortex microcontrollers. THE AIM OF CMSIS: Software reusability: make it easier to reuse code with different Cortex-M processors, reducing time to market and verification efforts.  Software compatibility: Due to consistent software infrastructure, software from various sources can work together, reducing the risk in integration.  The CMSIS allows easy access to processor core features from the c language.  CMSIS-compliant device drivers can be used with various compilation tools. CMSIS started out as a way to establish consistency in device-driver for the Cortex-M microcontrollers, and this has become CMSIS-Core. Since then, additional CMSIS projects have started: CMSIS-Core  A set of APIs for applications developers to access the features on the Cortex-M processor regardless of microcontroller devices and toolchain used. CMSIS-DSP library This library is intended to allow software developers to create DSP applications on Cortex-M microcontrollers easily. CMSIS-SVD the System View Description in an XMl-based file format to describe peripheral set in microcontroller products. CMSIS-RTOS  the CMSIS-RTOS is an API specification for embedded OS running on Cortex-M Microcontrollers. CMSIS-DAP the CMSIS-DAP(Debug Access Port) is a reference design for a debug interface adaptor, which supports USB to JTAG/Serial protocol conversions. The CMSIS files are integrated into device-driver library packages from the microcontroller vendor. So when you are using CMSIS-compliant device-driver libraries provided by the microcontroller vendors, you are already using CMSIS. We can define the CMSIS into multiple layers: Core peripheral Peripheral Layer Name definitions,address definitions, and helper functions to access core registers and core peripherals. This is processor specific and is provided by ARM. Device Peripheral Access LAyer:  Name definitions, address definitions of peripheral registers etc. This is device specific. Access Functions For Peripherals Access Functions For Peripherals How do I use CMSIS-Core ? Add Source files to the project. This includes: Device specific, toolchain-specific startup code, in the form of assembly or C. Device-specific device initialization code(e.g. System_c). Add header files into the search path of the project: A device-specific header