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Discussion Starter · #1 ·
It looks like I ran out of analog inputs in my Megasquirt Pro but I see in the instructions the below:

Analog (ADC) inputs over CAN This allows additional analogue inputs to be captured
from remote CAN devices and used with most MS3 features. The code allows up to 24 remote CAN
ADCs. The dropdown menus (e.g. EGT) allow you to select either a local ADC or a remote CANADC.
Before attempting to use the chosen CANADC, you need to enable it on this CAN settings menu. Due
to data sizes, the CANADCs are configured in groups of four. The exact table and offset numbers are
specific to the configuration of the remote device.


I have no clue what any of that is but it looks like I need some sort of external CAN device? What is this and how does it get hooked up to the Megasquirt?

Kevin
 

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It is an I/O expansion capability, Kevin. The MS3Pro provides eight (or is it 16?) built-in 0 to 5-volt analog inputs. If you have used all the analog i/o that the system provides you can bring in additional analog signals for EGT sensors, O2 sensors, accelerometers, vehicle ride height, or any of a variety of other metrics you want to measure.

An example of how it might be used with EGT sensors would be employing a multiplexor with millivolt-capable electronics to read each EGT sensor's output. The electronics in the thermocouple multiplexor would assign a unique can buss id to each EGT sensor and then report the measured voltage as a digital number that the ECU would decode into temperatures for each measured cylinder. By using a CAN bus interface, the I/O pins on the ECU can be reduced from many to only two!

The MS3Pro allows you to use the CAN bus to bring in the signals from many analog devices without using a dedicated I/O pin for each one. Instead, the device will use a gizmo that will translate the analog data streams from the individual devices into a digital signal and allow you to assign a CAN bus id to it for communication back to the ECU through the multiplexor. Check out §7.83, page 238 in the MS3Pro manual v1.205, and it will demonstrate the EGT sensor example. On page 240, they show how the CAN bus port numbering is assigned to each sensor.

I have attached a pdf document from 14Point7, which offers a very high-speed wideband O2 sensor. The document shows how their wideband sensors are connected to and identified on a CAN bus network.
 

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Discussion Starter · #3 ·
Under Generic Sensor Inputs there are 16 but from what I can tell beyond 5 analog sensors requires a CAN device.
When assigning an analog sensor there are only a few wires (Analog In 1, 2, 3, etc) that are identified on the large connector as pinouts with the proper wire to be used and from what I can tell I have used all these wires on sensors. For instance in the screenshot below although Analog In 2 isn't shown as being used in that table it's being used for a second O2 sensor elsewhere. So from what I'm concluding I'm out of wires that can be used for 0-5V sensors.

I hope I'm wrong because that CAN setup could be my bane unless I can find good vids on how to wire/program one up...

ks



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Discussion Starter · #4 ·
Randy at DIY got back with me and they confirmed I have used up all the analog inputs. They said the Microsquirt can be used for additional I/O's so I will review this option:


ks
 

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Randy confirmed that you are reading the tea leaves correctly, Kevin. What the Microsquirt does is essentially fulfill the function of the multiplexor I spoke of, taking a number of different sensor readings and multiplexing them into a data stream that it forwards up to the MS3Pro.
 

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Discussion Starter · #6 ·
It seems like a fairly simple way to do it so I plan to purchase it. I've read through some paperwork on it but still confused on some finer details so I will have to work through those during the install.

ks
 

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While I have not needed to use one yet, MalcolmV8 has used them and is quite familiar with how the two ECUs connect and communicate. You might want to give him a shout as you begin the project if you intend to use them.
 
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