CAN Bus Communications Decoded: Step 4: Program Devices to Transmit Required Data
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Step 4: Program Devices to Transmit Required Data
04.51
| 00:00 | Fourth step of the process is going to be programming our devices to transmit the required data. |
| 00:07 | Now in this instance it's going to be our Link ECU outputting that generic dash template onto the CAN bus. |
| 00:14 | So I'm just going to turn on our power supply here and you'll hear that fan ramp up again. |
| 00:18 | We've got some displays lighting up here so that's excellent, I know everything's receiving 12 volts like it should but currently nothing will actually be talking to each other because we don't have that CAN data on the network yet. |
| 00:32 | But if we pop over to my laptop I've got the Link configuration software open here. |
| 00:36 | And we'll just get connected to that ECU. |
| 00:39 | Now this has got a completely default profile loaded onto the ECU, just the one that it's been shipped with from the factory. |
| 00:47 | So there won't be any tuning information in here yet but I can still go ahead and set up the CAN transmission. |
| 00:53 | So for the Link software, that's actually under ECU controls and CAN setup here. |
| 00:59 | And then having read through the documentation for our Link ECU, I've actually hooked into the CAN bus wires that are part of, they call it the B connector on the Link ECU. |
| 01:09 | So it's this main connector here. |
| 01:11 | The Link Fury range of ECUs actually has 2 CAN bus interfaces. |
| 01:16 | Which can be a really valuable thing if you're dealing with devices that you can't change the transmission speed on for example and you've got 2 different devices that are at 2 different transmission speeds. |
| 01:27 | You can hook one up to each of the CAN buses on the Link, set its transmission speeds in those individual buses to the 2 different values and you can get all your communication working. |
| 01:37 | You can actually then use the Link ECU to pass information from one of those devices to the other. |
| 01:43 | But in this instance it's not what we're wanting to do. |
| 01:45 | But I am going to be wanting to configure the CAN 2 interface 'cause that's the one I've got our bus wires tapped into. |
| 01:53 | So I'm going to select that, I'm going to change the load from off to user defined 'cause I want to tell it how to operate. |
| 02:00 | So currently we can set up what are called a lot of different channels on our Link CAN setup here but I really only want one channel which is going to be that generic dash profile being transmitted out. |
| 02:14 | So I'm going to choose our channel one here and I'm going to change the mode to be transmit generic dash. |
| 02:24 | This one here, now I'm going to leave our ID set as the default of 1000 and you'll see that when Link has put in here a PID of 1000, it doesn't have 0X 1000 or 1000 followed an h, that tells me that that PID has actually been entered in decimal. |
| 02:44 | So we're in a decimal PID there of 1000. |
| 02:49 | Now that Link generic dash template is a compound message as well. |
| 02:53 | So we need to remember that and when we check on the other devices we're going to do quick checks just to make sure that they're set up to receive that compound message properly. |
| 03:01 | We've got a transmit rate here that we're going to need to define as well. |
| 03:06 | Thinking about transmitting crucial engine operating parameter, particularly things like engine RPM and manifold pressure, currently this is set to 1 Hz, that would be very very slow and wouldn't really give us usable data for a dash display so I'm going to change that to be 100 Hz. |
| 03:26 | Now we actually went through and worked out in an earlier module in the course, the bus load that transmitting this compound message profile out on at 100 Hz was going to give us and I know that's a bus load of around about 18% so we're well below our 80% cap there, we're going to have heaps of headroom on the bus if we need to put any other data on it as well. |
| 03:49 | So last thing I'm going to check is just that our bit rate is set and it is. |
| 03:54 | I like to use 1 Mb per second almost universally for my aftermarket electronics. |
| 04:00 | The only time I'll vary from that is if I'm dealing with a device where it's set at a slower speed and it can't be changed. |
| 04:07 | Then I'm forced to diverge from that. |
| 04:10 | I've not seen a speed setting of 1 Mb per second ever cause me any issues in a performance automotive setup. |
| 04:17 | So with that set we'll just recap, we've configured our CAN 2 here at 1 Mb per second, we're transmitting out our message at 100 Hz on PID 1000 and we are transmitting out the Link generic dash profile. |
| 04:33 | So I can go ahead and accept that and that's given me a nice reminder here to store my ECU settings which I'm going to do and that is going to complete the programming of our transmitting devices. |
