CAN bus wiring question - MS3PNP + Canchecked + AEM X-series
05-15-2023, 06:10 PM
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CAN bus wiring question - MS3PNP + Canchecked + AEM X-series
Hello,
I am trying to understand if and how I can have both the Canchecked display and the AEM X-series wideband both on CAN bus.
2002 NB w/ MS3pnp Pro
Currently my AEM WB is attached to my MS3's CAN inputs. It has been working great for the past year, no issues. I also have not installed a resistor aside from the internal resistor in the MS, which some say is an issue, and some say is OK according to other posts.
I want to add the Canchecked MFA 2.0 into my cluster for CLT, kPA (boost), RPM, MAT, AFR, and maybe one more.
Here are my options and I am wondering if one of these would work or if there is another way:
- Tap right in to the wires from the AEM gauge to the CANH and CANL (staggered of course).
- Get new CANH and CANL wires from the MS3 with a resistor on the end and then daisy chain in the AFR gauge and the Canchecked.
- Move the AEM gauge to another input and then just have Canchecked on CAN. I would prefer to keep the AEM on CAN though due to accuracy and reliability.
Here are posts I have found with some info, but nothing that answers my questions exactly:
Post about how AEM uses its own CAN protocol so CAN broadcasting needs turned off, where I believe Canchecked requires it to be on.
"Megasquirt CAN broadcasting has it's own protocol, which is what is used to communicate with CAN dashes or expansion like the TinyIOX. AEM uses a different protocol. If both were activated at the same time, there would be data conflicts. Thus if you use the AEM settings in your CANbus setup, you have to turn off CAN broadcasting."
https://www.miataturbo.net/mspnp-55/...2005-a-104360/
This confused me more, but at least I know about the channels I would need to configure if I add a device:
https://www.miataturbo.net/megasquir...estion-106087/
This looks to be what I am searching for, but with the first link I posted, can AEM and Canchecked be on the same bus then?
https://www.miataturbo.net/ecus-tuni...splays-106402/
About the resistor and wiring for my AEM gauge:
https://www.miataturbo.net/mspnp-55/...aem-ms3-98098/
Thank you!
I am trying to understand if and how I can have both the Canchecked display and the AEM X-series wideband both on CAN bus.
2002 NB w/ MS3pnp Pro
Currently my AEM WB is attached to my MS3's CAN inputs. It has been working great for the past year, no issues. I also have not installed a resistor aside from the internal resistor in the MS, which some say is an issue, and some say is OK according to other posts.
I want to add the Canchecked MFA 2.0 into my cluster for CLT, kPA (boost), RPM, MAT, AFR, and maybe one more.
Here are my options and I am wondering if one of these would work or if there is another way:
- Tap right in to the wires from the AEM gauge to the CANH and CANL (staggered of course).
- Get new CANH and CANL wires from the MS3 with a resistor on the end and then daisy chain in the AFR gauge and the Canchecked.
- Move the AEM gauge to another input and then just have Canchecked on CAN. I would prefer to keep the AEM on CAN though due to accuracy and reliability.
Here are posts I have found with some info, but nothing that answers my questions exactly:
Post about how AEM uses its own CAN protocol so CAN broadcasting needs turned off, where I believe Canchecked requires it to be on.
"Megasquirt CAN broadcasting has it's own protocol, which is what is used to communicate with CAN dashes or expansion like the TinyIOX. AEM uses a different protocol. If both were activated at the same time, there would be data conflicts. Thus if you use the AEM settings in your CANbus setup, you have to turn off CAN broadcasting."
https://www.miataturbo.net/mspnp-55/...2005-a-104360/
This confused me more, but at least I know about the channels I would need to configure if I add a device:
https://www.miataturbo.net/megasquir...estion-106087/
This looks to be what I am searching for, but with the first link I posted, can AEM and Canchecked be on the same bus then?
https://www.miataturbo.net/ecus-tuni...splays-106402/
About the resistor and wiring for my AEM gauge:
https://www.miataturbo.net/mspnp-55/...aem-ms3-98098/
Thank you!
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05-18-2023, 01:55 PM
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I would suggest using one of these bad boys: https://www.aemelectronics.com/produ...aemnet-can-hub. It is so nice to just plug and unplug things into the bus at will with DTM connectors. Your first option should also work fine.
The CANChecked gauges have internal resistors you can toggle on/off at will. You can also change the bus speed to use so make it match whatever you have set in your CAN settings. From reading and personal experience I've found that the need for the resistor depends on the length of the CAN bus wires. In my own car, using a Spartan 3 wideband controller and a CANChecked gauge on the same bus I can enable the resistors on both devices, disable the resistors on both, enable one or the other, and there is no change in behavior. The ECU does have a terminating resistor that's always on. The CANChecked gauge worked great on MS3 for me.
So the TLDR is you should be able to do what you want, it may take some fiddling with settings in the gauge/ecu.
The CANChecked gauges have internal resistors you can toggle on/off at will. You can also change the bus speed to use so make it match whatever you have set in your CAN settings. From reading and personal experience I've found that the need for the resistor depends on the length of the CAN bus wires. In my own car, using a Spartan 3 wideband controller and a CANChecked gauge on the same bus I can enable the resistors on both devices, disable the resistors on both, enable one or the other, and there is no change in behavior. The ECU does have a terminating resistor that's always on. The CANChecked gauge worked great on MS3 for me.
So the TLDR is you should be able to do what you want, it may take some fiddling with settings in the gauge/ecu.
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05-18-2023, 02:12 PM
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Awesome, thanks so much for this!
I'll plan to use the CANChecked device's resistor as the terminator then and chain in the AEM gauge. I'll use that 4-port if I expand it more.
It sounds like I should be able to have both the 11-bit CANChecked and 29-bit AEM gauge on the same bus and it should still work with MS.
Thanks!
I'll plan to use the CANChecked device's resistor as the terminator then and chain in the AEM gauge. I'll use that 4-port if I expand it more.
It sounds like I should be able to have both the 11-bit CANChecked and 29-bit AEM gauge on the same bus and it should still work with MS.
Thanks!
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05-19-2023, 03:42 PM
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The MS can talk to EITHER, but not BOTH if that makes sense...
This was a HUGE reason I went with the Spartan 3 wideband over the AEM because AEM doesnt speak normal CAN... Its ok if thats the only CAN item you want to run, or if you want to run exclusively AEM devices, but throw something else out there and you are out of luck. I want to run an AIM dash eventually which runs normal CAN. The purpose of CAN was to make it universal and then you have AEM come in and try to reinvent the CAN protocol.
I am running an AEM oil pressure gauge/sensor that has CAN output, but I am using the 0-5v for the MS3 as oil pressure isnt as critical for the MS3 as wideband is.
To do what you want you would have to ditch the AEM setup and move to something else like the Spartan 3 and get away from AEM's proprietary CAN protocol.
I also agree with you that you want your WB O2 on CAN as its much more accurate and faster than 0-5v and since the MS3 actually uses it for fueling you want the best signal you can get.
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10-25-2023, 08:26 PM
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Yes, you can. The CANchecked gauge will parse 11-bit CAN broadcasts from the MS3 and the MS3 will parse 29-bit CAN broadcasts from the AEM gauge. Note that you will have to disable the “29bit MegaSquirt CAN Enable” option in the general CAN settings. This is unrelated to normal 29-bit CAN as broadcasted by the AEM gauge and instead refers to the custom 2-way MegaSquirt CAN protocol. If you don’t have any devices that use that oddball protocol (you almost certainly don’t), then you’re good to go.
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10-25-2023, 08:38 PM
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Yes, you can. The CANchecked gauge will parse 11-bit CAN broadcasts from the MS3 and the MS3 will parse 29-bit CAN broadcasts from the AEM gauge. Note that you will have to disable the “29bit MegaSquirt CAN Enable” option in the general CAN settings. This is unrelated to normal 29-bit CAN as broadcasted by the AEM gauge and instead refers to the custom 2-way MegaSquirt CAN protocol. If you don’t have any devices that use that oddball protocol (you almost certainly don’t), then you’re good to go.
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10-25-2023, 10:58 PM
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NO, not as far as I know.
The MS can talk to EITHER, but not BOTH if that makes sense...
This was a HUGE reason I went with the Spartan 3 wideband over the AEM because AEM doesnt speak normal CAN... Its ok if thats the only CAN item you want to run, or if you want to run exclusively AEM devices, but throw something else out there and you are out of luck. I want to run an AIM dash eventually which runs normal CAN. The purpose of CAN was to make it universal and then you have AEM come in and try to reinvent the CAN protocol.
I am running an AEM oil pressure gauge/sensor that has CAN output, but I am using the 0-5v for the MS3 as oil pressure isnt as critical for the MS3 as wideband is.
To do what you want you would have to ditch the AEM setup and move to something else like the Spartan 3 and get away from AEM's proprietary CAN protocol.
I also agree with you that you want your WB O2 on CAN as its much more accurate and faster than 0-5v and since the MS3 actually uses it for fueling you want the best signal you can get.
The MS can talk to EITHER, but not BOTH if that makes sense...
This was a HUGE reason I went with the Spartan 3 wideband over the AEM because AEM doesnt speak normal CAN... Its ok if thats the only CAN item you want to run, or if you want to run exclusively AEM devices, but throw something else out there and you are out of luck. I want to run an AIM dash eventually which runs normal CAN. The purpose of CAN was to make it universal and then you have AEM come in and try to reinvent the CAN protocol.
I am running an AEM oil pressure gauge/sensor that has CAN output, but I am using the 0-5v for the MS3 as oil pressure isnt as critical for the MS3 as wideband is.
To do what you want you would have to ditch the AEM setup and move to something else like the Spartan 3 and get away from AEM's proprietary CAN protocol.
I also agree with you that you want your WB O2 on CAN as its much more accurate and faster than 0-5v and since the MS3 actually uses it for fueling you want the best signal you can get.
https://www.jegs.com/InstallationIns...17-30-7106.pdf
Megasquirt 29-bit CAN is what does not speak normal CAN, that is it's own special protocol that is enabled by the "29bit Megasquirt CAN Enable" option. This is truly reinventing CAN. It is this protocol that is incompatible with AEMnet and, more generally, all other 29-bit CAN messaging schemes.
So, in theory, MS3 should be perfectly happy broadcasting 11-bit realtime CAN data for the CANchecked gauge while receiving EGO data via 29-bit CAN from the AEM X-Series wideband. That's not to say that the firmware is wonky and for some reason does not support this, but as long as "29bit Megasquirt CAN Enable" is off, it should work just fine.
Some further evidence:
This is the specification for the CAN message the 30-0300 broadcasts...
And this perfectly normal CAN receiving setup should happily retrieve the lambda value (although I am unsure of exactly what form the MS3 expects this to be in, so the mult/div/add may need to be tweaked):
Last edited by intenseapple; 10-25-2023 at 11:16 PM.
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