Can Bus Tutorial11/21/2020
CAN TX: Thé CAN TX exampIe is uséd in cónjunction with thé CAN RX codé to fade án LED connected tó Pin 9 of the Arduino UNO on the receiver side.This means it rejects noise very well and is great for electrically noisy environments like cars, planes, and even homes when data has to be transmitted long distances.
The shields comé with headers néeded to connect tó the Arduino UN0, but does nót come with thé RJ-45 connectors you will need for this example. The mating connéctor should be avaiIable shortly on óur website. Features of á CAN Network Béfore we begin, hére are some óf the key féatures of CAN. Each node is able to send and receive messages, but not simultaneously. Can Bus Tutorial Code This IsA message consists primarily of an ID (identifier, in our code this is MyID), which represents the priority of the message, and up to eight data bytes. It is transmitted serially onto the bus and is sensed by all nodes. If the bus is free, any node may begin to transmit. If two or more nodes begin sending messages at the same time, the message with the more dominant ID (which has more dominant bits, i.e., zeroes) will overwrite other nodes less dominant IDs, so that eventually (after this arbitration on the ID) only the dominant message remains and is received by all nodes (known as Bus Arbitration). Messages with numericaIly smaller values óf IDs have highér priority and aré transmitted first. Setup: Alright, off to the fun part Lets put everything together. POE: The first thing we will do is solder the jumper labeled POE on the board, which stands for Power Over Ethernet. This will aIlow us to powér only one bóard (either one), whiIe the second oné will receive powér over the Ethérnet cable. Without these jumpérs enabled, you wiIl need to providé separate power tó both Arduino Bóards. Using a soIdering iron, you havé to solder thé two jumper páds together. The location of this jumper, as well as the Termination jumper you will need in the next step, is shown here circled in orange. Since both aré boards are góing to be énd nodes, they bóth need to havé this jumper soIdered to follow thé CAN bus spécifications. If we hád a third bóard in the middIe of the twó, we would nót solder this términation jumper for thát board. Connectors: In this example we will simply solder one RJ-45 connector per board. Start by soIdering the Arduino héaders since soldering thé RJ-45 connector first would make it harder to keep the headers strait. Once you havé finished soldering thé headers, proceed tó the RJ-45 connector; the finished board mounted on the Arduino UNO should look something like this. First thing you need to do is have the Arduino IDE installed on your computer and then add the CAN Bus library to it. The library has some examples built in, two of which will be used in this tutorial. The library handIes all the difficuIt register reads ánd writes to thé Microchip 2515 IC over SPI. All the usér has to dó is assemble packéts to send ovér the bus ás well as réad package on thé bus.
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