Join Dave and Bob as they explore the similarities and differences between two key serial interface protocols, Controller Area Network (CAN) and RS-485.
I think the key point to mention is that RS-485 is just an electrical specification and not a communication protocol. While CAN bus has an electrical specification and a communication protocol (IE the format of a CAN frame).
exactly. And the crucial part of CAN is how the protocol handles collisions without re-transmissions. That's important for controllers in cars: the data from the top priority device is never delayed. CAN frames start with arbitration bits. The standard requires that each bit spans the whole length of the bus wires. Hence, the devices can figure out which one has higher priority while they are sending the arbitration bits. That's also what limits the bus to 40m at 1Mbps - the bits propagate through the bus wires at the speed of light.
Dr. Andeen. hello hello. Nice vid. Just used a ton of Maxim 485 units inside my camper conversion Sprinter to measure and control all kinds of stuff. Maxim makes it work.
The difference (roughly) is that a 485 message consists of a bunch of independent 11 bit characters, each with their own framing bits, whereas a can message has all 40-something payload bits, including error correction bits, crammed together between one set of framing bits.
CAN frame header contains arbitration bits to avoid collisions and allow the top priority device to send its data without re-transmissions. To make it work, CAN requires each bit to occupy the whole length of the bus wires. Bits spread through the bus at the speed of light. Hence the limit of 40m at 1Mbps.
The pity about CAN is, it's timing design in an application is a nightmare. How about FLEXRAY? Or about keep sticking to ARCNET-Protocol stack over RS485 lines instead of CAN? Or BACnet over RS-485 perhaps? Do you offer a ARCNET over RS-485 chip/chipset perhaps? I should take a look at your site, I guess...
Due to not haveing a facny ESD gun we use a BBQ lighter instead. Could you show the difference between an ESD gun KV and a BBQ lighter? We even just rub or feet on the floor to make some ESD.
@@Ender_Wiggin well if you need that much specific details, it's not hard to make a few kv discharge switching transformer device. Use that to store a dc voltage In a cap. You should exactly what's coming out.
As far as I can tell, other than the basic analog copper cable, any interface has its own protocol e.g. USB interface (all iterations of them) have their own protocol of communication, as serial port, parallel port, etc even thought that the various interfaces can have various protocols every single one has at least a protocol...
I think the key point to mention is that RS-485 is just an electrical specification and not a communication protocol. While CAN bus has an electrical specification and a communication protocol (IE the format of a CAN frame).
exactly. And the crucial part of CAN is how the protocol handles collisions without re-transmissions. That's important for controllers in cars: the data from the top priority device is never delayed. CAN frames start with arbitration bits. The standard requires that each bit spans the whole length of the bus wires. Hence, the devices can figure out which one has higher priority while they are sending the arbitration bits. That's also what limits the bus to 40m at 1Mbps - the bits propagate through the bus wires at the speed of light.
Could you link to the data sheets?
Dr. Andeen. hello hello. Nice vid. Just used a ton of Maxim 485 units inside my camper conversion Sprinter to measure and control all kinds of stuff. Maxim makes it work.
Why you did not zoom and show the screen of oscilloscope closely. I think, its important to show the scope screen, then the engineer's face.
An important difference to point out would be the protocol: are the framing bits significantly different between the protocols?
The difference (roughly) is that a 485 message consists of a bunch of independent 11 bit characters, each with their own framing bits, whereas a can message has all 40-something payload bits, including error correction bits, crammed together between one set of framing bits.
CAN frame header contains arbitration bits to avoid collisions and allow the top priority device to send its data without re-transmissions. To make it work, CAN requires each bit to occupy the whole length of the bus wires. Bits spread through the bus at the speed of light. Hence the limit of 40m at 1Mbps.
Very nice!
The pity about CAN is, it's timing design in an application is a nightmare. How about FLEXRAY? Or about keep sticking to ARCNET-Protocol stack over RS485 lines instead of CAN? Or BACnet over RS-485 perhaps?
Do you offer a ARCNET over RS-485 chip/chipset perhaps? I should take a look at your site, I guess...
Due to not haveing a facny ESD gun we use a BBQ lighter instead. Could you show the difference between an ESD gun KV and a BBQ lighter? We even just rub or feet on the floor to make some ESD.
Just estimate it from the max spark gap. Just don't heat solder your PCB boards on the BBQ grill.
@@preddy09 that will tell you the job not the energy
@@Ender_Wiggin well if you need that much specific details, it's not hard to make a few kv discharge switching transformer device. Use that to store a dc voltage In a cap. You should exactly what's coming out.
Why does this video look like its from the 90's?
Is that a 3.5" floppy drive on the center scope?
This looks like....whos line is it anyway?
What does "ip" stand for at 4:25?
Andrii, I am pretty sure it stands for intellectual property.
IP is the protection grade defined in IEC 60529
@@cristianriverafierro4887 Here "V" is missing, it should be VIP: Very Important Person", like PM, President, Chief Justice, etc.
CAN vs. RS-485: What's the Difference? the first one is protocol, the second one is interface? right?
As far as I can tell, other than the basic analog copper cable, any interface has its own protocol e.g. USB interface (all iterations of them) have their own protocol of communication, as serial port, parallel port, etc even thought that the various interfaces can have various protocols every single one has at least a protocol...
485 is only an electrical standard. Nothing more :)
Part Number?
Raspberry Pi RS485 and CAN Module: czcams.com/video/nAYsmBIwneQ/video.html
More nodes @ 3 Meters