STM32 CAN Communication || NORMAL Mode

Summary

This tutorial delves into the intricacies of CAN communication between two devices, using the Blue Pill and F446RE microcontrollers. It covers the setup, including connections and resistors, and explains configuring the CAN peripherals in CubeMX. The script guides through coding, including setting transmission parameters, handling interrupts, and filtering. The practical demonstration shows how to send and receive messages, control LEDs based on received data, and ensure continuous communication without manual intervention, highlighting the efficiency of CAN for embedded systems.

Takeaways

• 😀 The tutorial is a continuation of a series on the CAN (Controller Area Network) protocol, focusing on communication between two CAN devices.
• 🔌 The video demonstrates the hardware setup required for CAN communication, including connections for RX, TX, CAN high, CAN low, and the importance of a 120 ohms resistor at each node.
• 🔩 It's crucial to check if the transceiver breakout board has the necessary 120 ohms resistance, as some do not and require manual connection.
• 🔄 The script explains the software setup using STM32 microcontrollers, specifically the Blue Pill and the F446RE, and the use of CubeMX for configuration.
• 📈 The video covers configuring the CAN peripherals, setting the baud rate to 500,000 bits per second, and the distinction between CAN1 as master and CAN2 as slave.
• 🛠️ The tutorial includes programming steps涉及for transmitting data, such as setting up an interrupt for the RX0, using FIFO for message storage, and handling notifications for data pending in the RX FIFO.
• 💡 The purpose of the project is outlined: the F446RE sends data bytes that control the delay and blink count of an LED on the Blue Pill, which is then mirrored on the F446RE after reception.
• 🔄 The script details the process of sending and receiving messages, including the use of callback functions for handling transmission and reception of data.
• 🛡️ The importance of filter configuration for message passing is emphasized, with specific settings demonstrated for allowing certain IDs through the filter banks.
• 🔧 The video provides practical advice for avoiding confusion with SD card links when connecting multiple controllers to the same computer.
• 🔧 The tutorial concludes with a demonstration of the working system, showing the LED blinking according to the received CAN messages and the data flow captured by an analyzer.

Q & A

What is the purpose of this tutorial video?

The purpose of this tutorial video is to demonstrate how to communicate between two CAN (Controller Area Network) devices using microcontrollers.

What should viewers do before watching this video?

Viewers should watch the previous video on the basics of the CAN protocol before watching this one, as it provides necessary foundational knowledge.

What microcontrollers are used in this tutorial?

The tutorial uses the Blue Pill and the F446RE microcontrollers for the demonstration.

What is the significance of the 120 ohms resistance in the CAN connection?

The 120 ohms resistance is crucial in the CAN connection as it is connected at each node to ensure proper termination and signal integrity.

How are the CAN high and CAN low wires connected in the setup?

The CAN high and CAN low wires are connected with each other using a twisted pair to minimize electromagnetic interference.

What is the board rate set to in the CAN configuration?

The board rate is set to 500,000 bits per second in the CAN configuration.

Which CAN peripheral is configured as the master and which as the slave in the video?

CAN1 is configured as the master CAN, and CAN2 is configured as the slave CAN in the video.

What is the purpose of the onboard LED and user button in the project setup?

The onboard LED is used for visual feedback, and the user button is used to trigger the sending of CAN messages when pressed.

How many data bytes can be sent in a single CAN message according to the video?

Up to 8 data bytes can be sent in a single CAN message.

What is the role of filters in the CAN communication setup shown in the video?

Filters allow message filtering at the hardware level, reducing the CPU workload by only allowing specific messages to be processed.

How can the communication process be automated without manual button presses?

The process can be automated by sending data after the LED blinking is finished, as demonstrated with the Blue Pill setup, allowing continuous communication without manual intervention.

Outlines

00:00

🔌 Setting Up CAN Communication with Microcontrollers

This paragraph introduces the tutorial on establishing CAN (Controller Area Network) communication between two devices, using the Blue Pill and the F446RE microcontrollers. It emphasizes the importance of watching the previous video for understanding the basics of the CAN protocol. The connection setup is detailed, including the use of transceivers, the necessity of 120-ohm resistance at each node, and the correct wiring for CAN high and low. The video also mentions checking the presence of the resistance on the breakout board and setting up the microcontroller pins for communication.

05:11

🛠 Configuring CAN Peripherals and Project Setup

The second paragraph focuses on configuring the CAN peripherals using STM32CubeMX for the F446RE microcontroller. It explains the selection of an external crystal for the clock, setting the system to run at 180 MHz, and configuring CAN1 as the master CAN with a baud rate of 500,000 bits per second. The tutorial also covers setting the operating mode to normal, using FIFO zero for storing incoming messages, and enabling the RX0 interrupt in the NVIC. Additionally, it describes setting up the onboard LED and external interrupt for a user button, and generating the project with the necessary configurations.

10:13

📶 CAN Data Transmission and Reception Process

This paragraph delves into the process of data transmission and reception in CAN communication. It describes how the F446RE will send two data bytes, one for delay and the other for the number of LED blinks on the second board. The transmission is handled in the XD callback function, triggered by a user button press. Upon receiving a message, the F446RE processes it, and if the data length is two bytes, it sets a flag to blink the LED accordingly. The paragraph also covers configuring CAN filters to allow specific IDs to pass through and storing incoming messages in FIFO zero.

15:14

🔄 Demonstrating CAN Communication with Microcontrollers

The final paragraph demonstrates the practical implementation of the CAN communication setup. It shows the creation of another project for the Blue Pill, configuring it similarly to the F446RE but using FIFO one for message reception. The tutorial explains copying and adapting the code from the F446RE project, including the transmit ID and the filter configuration. It also discusses assigning the correct SD links to each microcontroller to avoid confusion and concludes with a live demonstration of the LED blinking according to the CAN messages exchanged between the microcontrollers, showcasing the successful implementation of CAN communication.

Keywords

💡CAN Protocol

The CAN (Controller Area Network) Protocol is a communication protocol designed for reliable real-time communication in vehicle and industrial environments. It allows microcontrollers and devices to communicate with each other using a single twisted pair cable. In the video, the CAN protocol is the central theme as the tutorial explains how to set up and use it for communication between two CAN devices.

💡Transceiver

A transceiver is a device that can both transmit and receive signals. In the context of the video, the transceiver is used to interface the CAN devices with the physical CAN bus. The script mentions connecting the RX and TX pins of the transceiver to the respective microcontrollers, which is essential for setting up the CAN communication.

💡120 Ohms Resistance

The 120-ohm resistance is a term used in the video to describe the termination resistors that are necessary on a CAN bus at each end of the network. These resistors help to dampen the signal reflections and maintain signal integrity. The script specifies that this resistance must be connected at each node of the CAN bus.

💡Twisted Pair

A twisted pair refers to a type of wiring in which two conductors are twisted together for the purpose of improving electromagnetic compatibility and reducing crosstalk. In the script, the instructor recommends twisting the wire pair connected between CAN high and CAN low to potentially improve communication reliability.

💡CubeMX

CubeMX is a configuration tool for STM32 microcontrollers that allows users to configure the microcontroller's peripherals and generate code. In the video, CubeMX is used to set up the CAN peripherals, configure the clock, and generate the initial project setup for the STM32F446RE and Blue Pill microcontrollers.

💡FIFO (First In, First Out)

FIFO, standing for First In, First Out, is a method of organizing data in a queue where the first data to be stored is the first to be retrieved. In the context of the video, the CAN peripherals use FIFO to store incoming messages, which is configured in CubeMX and utilized in the program to handle received data.

💡NVIC (Nested Vectored Interrupt Controller)

The NVIC is a part of the ARM Cortex microcontroller architecture that manages and prioritizes interrupts. In the video, the NVIC is configured to enable the RX0 interrupt, which is used to handle incoming messages in the CAN communication setup.

💡CAN Filter

A CAN filter is used to selectively allow certain messages to be received by a CAN device based on their identifiers. In the script, the instructor configures filters to allow only specific messages to pass through to the CAN peripherals, demonstrating how message filtering can be done at the hardware level.

💡SD Link

The SD (Serial Debug) Link is a feature that allows a debugger to connect to a microcontroller for debugging purposes. In the video, the instructor discusses assigning the SD link to the respective controllers to avoid confusion when connecting both controllers to the same computer.

💡Data Bytes

Data bytes refer to the actual payload of a CAN message, which can be up to 8 bytes long. In the video, the script describes how the first data byte is used as a delay for the LED on the second board, and the second data byte determines the number of times the LED will blink, illustrating the use of data bytes in a CAN message.

💡CAN Analyzer

A CAN Analyzer is a tool used to monitor and analyze CAN bus traffic. In the video, the CAN Analyzer is connected to observe the data flow between the two microcontrollers, providing a visual representation of the messages being sent and received.

Highlights

Introduction to part 2 of the CAN protocol tutorial focusing on communication between two CAN devices.

Prerequisite knowledge of the basics of the CAN protocol from a previous video.

Hardware setup using the Blue Pill and F446RE controllers with specific pin connections.

Explanation of the importance of 120 ohms resistance at each CAN node.

Demonstration of twisted pair wiring for CAN high and low connections.

Powering the transceivers with 5 volts from the microcontrollers.

Configuration of the CAN1 as the master and CAN2 as the slave in CubeMX.

Setting the baud rate to 500,000 bits per second for CAN communication.

Enabling the RX0 interrupt and configuring the onboard LED and user button in the Nucleo project.

Programming the transmit and receive data arrays and variables for the TX mailbox.

Explanation of the data transmission process and the role of the DLC, Standard ID, and the ID of the sender.

Implementation of the XD callback function for data transmission upon user button press.

Reception of CAN messages and the use of a message pending callback function.

Filter configuration within the CAN initialization function for message filtering.

Assignment of SD links to their respective controllers to avoid confusion.

Creation of a project for the Blue Pill with similar settings and code structure.

Demonstration of the communication process with LED blinking according to received data.

Use of an analyzer to observe the data flow and message structure in real-time.

Adjustment of data bytes to change the LED blinking behavior and observation of the effects.

Continuous communication process without manual intervention by sending data after blinking completion.

Conclusion summarizing the use of CAN for communication, benefits of filters, and availability of code download.

Transcripts

hello

everyone welcome to controllers tech

this is part 2 of the tutorial on can

peripheral and today we will see how to

communicate between

two can devices i have already covered

the basics of the can protocol

and you must watch that video before

this one

you can see the video on the top right

so let's start with this video now

i am using the blue pill and the f446re

controllers

and the connection is as shown here the

rx and the tx pins from the transceivers

are connected to the respective

microcontrollers

then can high and can low are connected

with each others

note that there must be a 120 ohms

resistance connected at each node

just as it is shown in figure some

transceivers have this resistance on the

breakout board itself

and other don't so make sure you check

the resistance

here is how the connection is i have

twisted the wire pair connected between

can high and can low

you could try with simple wires but if

doesn't work

try twisted pair here is the 120 ohms

resistance connected between the can

high

and low i have it connected on the other

node too

p11 and p12 from blue pill are connected

to the first transceiver

and the same pins from nucleo are

connected to the second transceiver

the transceivers are powered with 5

volts from the microcontrollers

this is all about the connection now

let's start the project for the nucleo

first

so here we are in the cube mx

first of all i am selecting the external

crystal for the clock

i have eight megahertz crystal and i

want the system to run at maximum 180

megahertz

notice here that the four four six f2

can peripherals

as mentioned in the reference manual the

can one is the master can

and the can 2 is the slave can

also they have 28 filter banks all

together

let's configure the can one

now here i am going to set the board

rate to 500

000 bits per second

i am just modifying these parameters to

get that

here i got the board rate

now make sure that the operating mode is

set to normal

and i am going to use fifo zero to store

the incoming message

so in the nvic i am enabling the rx0

interrupt

this is it for can setup now i am

setting the pa5 as output for the

onboard led

also i am selecting the external

interrupt for the user button

which is connected to the pc13

this is it now click save to generate

the project

i hope you remember things from previous

video because i am going to skip some

explanation here

let's write the program now this is

where the transmit header data will be

stored

rx header will store the header from the

incoming message

let's create the arrays to store the tx

data

and the rx data

and at last the variable for the tx

mailbox

now in the main function start the cam

activate the notification for the data

pending in the rx fifo

everything i am doing has already been

covered in the previous video

kindly watch it if you don't understand

something here

after activating the notification we

will load data in the tx header

i am going to send 2 data bytes so dlc

is 2.

we will be using standard id and the id

will be 0 cross

446 this is the id of f446re

whenever this controller will send the

message this id

will act as the id of the sender now

before i send data

let me explain what i actually want to

achieve here

this controller will send the two data

bytes

the first data byte will act as delay

for the led on the second

board and the second data byte will act

as the number of times

that led will blink when the second

controller receives this message

the led on it will blink according to

these instructions

i am not going to send the data here but

instead let's send it in the xd callback

function

when the user button is pressed this

function will be called

and we will send the data here

the delay will be 100 milliseconds

and the loop will be repeated 10 times

now we will send the data using hull can

add tx message

here we have activated the notification

for the receive

when this controller will receive

message from the blue pill

a message pending callback will be

called

inside this callback we will receive the

data from the fifo

zero the header will be stored in rx

header

and the data will be stored in the rx

data

let's create a flag

we will just do one more check if the

data length is two bytes

then the flag will set

if the flag is set we will blink the led

the number of times it will blink will

be the second byte of the rx data

and the time delay will be the first

byte

and finally reset the flag so that there

is no false blink

let's build it once

i think i forgot to enable the interrupt

for the xd line

let's enable it

next we have to configure the filters

we will configure inside the can

initialization function

here is the filter configuration that i

am

using enable the can filter

i am assigning 20 filter banks to the

can one

out of these 20 i am using filter bank

number 18.

this is the id that should pass through

this id will be assigned to the blue

pill later

and the same value in the mask id

register also

i am using fifo 0 to store the incoming

message

this configuration is explained in the

previous video

so make sure you watch it let's build it

now

now since i am going to connect both the

controllers to the same computer

i don't want the sd links to mix up so i

am going to assign the respective sd

links to their controllers

right now i have connected only the f446

and if i scan the sd link here it will

only show one

so we will keep this sd link assigned to

this board

that's all for this now let's create

another project for blue pill

i am doing the basic setup and running

the system at maximum clock

activate the can peripheral we have to

select the same board rate here

that is 500 000 bits per second

here i will use the fifo 1 for receiving

the message

this is just to demonstrate pc 13 is the

led on board

so select it as output that's it

click save to generate the project

i am going to use same code that i used

in 446

so copy everything from here

we are not using the external interrupt

in blue pill

let's copy this part now

here we don't have can one or can two

instead it's just

can as i said i am using

fifo one here so replace all fifo zero

with fifo one

the transmit id for blue pill will be

zero cross one

zero three

now let's copy the while loop

here the led is pc13

now since we are not using the external

interrupt here

we will send the data in this loop

itself

let's define the data that we will send

and after the led is finished blinking

we will send the data using

hollard tx message

now copy the filter configuration

here the start slave bank does not

matter

like i explained in the previous video

and the filter bank should be between 0

to 13.

the id that will be allowed to pass is 0

cross 4 446

the id of the f4 controller

ok this should be can and we are using

fifo one

all right it's correct now so i have

removed the f4 sd link

and now only the blue pill is connected

if we scan the sd link only one shows up

and we will assign it to the blue pill

now the code has been loaded into both

the microcontrollers

let's see if it works as expected

i have also connected the analyzer to

see the data flow

channel 0 is connected to the tx of 446

and channel 1 is connected to the tx of

blue pill

pay attention to the leds on both the

microcontrollers

the communication will start only when

the button on the 446 is pressed

as you can see when i press the button

the led on blue pill blinks for some

time

and then the led on 446 starts blinking

and then everything stops until the

button is pressed again

this is exactly what we programmed it to

do

let's see the data this is the message

sent by

four four six you can see the id

the control field the two data bytes

once this message is received by the

blue pill the led will blink

and once the led finished blinking the

blue pill will send the message

and here you can see the message sent by

blue pill

you can see the same process will repeat

every time we press the button

let's try changing the data for both of

them

you can see the led is blinking somewhat

longer now

also observe the message on the analyzer

there is almost a delay of four seconds

here

we are sending the 100 milliseconds

delay and 40 times blink to the blue

pill

and that's why this 4 seconds so this

works pretty good

now if you don't want to press the

button every time you can just send this

data

after the blinking is finished just like

we are doing in the blue pill

this way the process will keep going

forever without any manual intervention

let's run it now

i will start the process by pressing the

button once

you can see the led on blue pill is

blinking

and now the led on the 446

and this process is keep repeating by

itself

this is how we can use the can for the

communication

we can send up to 8 data bytes at a time

filters allow the message filtering at

the hardware level itself

so the cpu don't have to do that work

this is it for this video i hope you

guys understood the can protocol

and how to use it for communication

filter configuration is covered in the

previous video

so watch it if you haven't watched it

yet

you can download the code from the link

in the description

keep watching and have a nice day ahead