M2 Hardware Changes

I wanted to get the conversation started on changes to the M2 platform. We will be making mid cycle updates to further improve upon the usability of M2. These changes will be small to medium size tweaks. We will not be replacing the processor, but smaller board changes are not out of the question.

Please respond if you have suggestions, wants, or demands.

I will then add any changes we plan on making to this top post:

  1. LDO on the processor board upgrade
  2. Change the 24 pin connector to a 16 pin connector so it is harder to shove the wrong side in when working with the UTH interface
  3. add Jtag connector
  4. Add solder jumper to select either 3.3V OR 5V to XBEE socket

Timeline: TBD

There was a suggestion to remove a component to allow the M2 to read the voltage of the 12 volt supply. Apparently there was something added as protection that wasn’t actually needed that prevents the reading of the voltage of the system.

Would be nice if that were removed or changed in a manner to allow the voltage to be read up to normal “running” voltage.

Also on the break out board, although not directly related, can you provide these with a header already soldered on? would be much easier to connect other devices to it if it came with a header presoldered on the board. if people want to still solder something onto it they can onto the bottom of the pins.

There was also a request for support for a battery connection to allow for a RTC. While installing a full battery onboard may be impractical perhaps having a connector where one could be connected would be reasonable.

I just heard from someone about a request for a hopefully simple modification.
In Australia they still have ALDL equipped vehicles which is on pin #9. Should be easily to duplicate on the M2. Would require one of the 12 volt outputs and a 12volt input to be connected in parallel to the pin. Just not sure yet if it would be sink or source. It could be made an optional addition by just adding a couple traces and a solder pad. Would allow easy adding the port if necessary. So the circuit would be open if no solder. If solder then it would tie the 12volt input, 12volt output and pin #9 together. Currently pin 9 is a test point.

Other than onboard fuses that can be easily replaced on the Input/Output section those are the only things that come to my mind.

I also recall this suggestion that we add special function pins for programming.

@fenugrec can you describe these special function pins or send us a link to an ideal set up?

Hi Modifications/Upgrades as per previous post suggestions

1, Add 2 solder pads to the CPU board to enable wires to be soldered to the processor board for the addition of an external RTC battery backup. This will also require the removal of R12 0 ohm resistor & addition of 2 small signal diodes to prevent charging of the battery from the power supply & also discharge of the battery into other parts of the circuit other than the RTC battery input.

  1. Removal of the zener protection diode D2 off the CPU board to enable correct reading of the Vehicle supply voltage,

Yes, you need to refer to the J2534 standard . Either the most recent published by SAE ($$ unless you can find it at a local university / library, that’s what I did), or the older 2002 version that was adopted as US law. Search on archive.org , I forget the link.

To be strictly compliant, it’s actually not trivial - here’s an excerpt of part (6.7) :
a. Minimum 5 V DC
b. Maximum 20 V DC
c. Resolution 0.1V DC
d. Accuracy ±2% of requested voltage
e. Maximum source current 150 mA
f. Maximum sink current 300mA (only for SHORT_TO_GROUND on pin 15).
g. Maximum 1 ms settling time (required for SCI protocol only, reference SAE J2610 Information
h. Pin assignment software selectable

I had done a few design iterations for the analog part of this (including 40V tolerance etc) but put it on standby for a while. It would ideally need maybe a SEPIC converter servo’d by a DAC; or a boost + buck combination (also with DAC control).

I’d like to see you consider changing the input to CAN0 (on J1962 pins 6 and 14). The 100pF capacitors C31 and C32 installed now are the maximum capacitance allowed for any node by ISO15765-4. I feel that the 100 ohm + 560pF AC termination specified for external test equipment would be better for most users.

In addition to what I mentioned before I would like to mention the suggestion I made before that would allow a 1 skew M2.

Put a double row header prior to the ODBII connector with each pin connected to one pin on the plug side of the header and the other side connected to whatever traces currently go to them. Spacing the same as a ribbon cable. This would allow someone to be able to re assign the pins to different ports but also allow someone to use as a UTH version. Would require minimal extension of the board since you currently have the board setup for both connectors now.

These are all great ideas. Thanks for helping me compile some of the old ones that came up before. Keep them coming as you think of them. I don’t have a timeline yet on when we will be making these changes. Right now the question is which ones should we tackle next.

We are also playing with the idea of adding more products to the M2 line up. The main thought is we have a lot going on already on that board and most people aren’t using everything. Might be as simple as depopulating some of the less used parts to make a beginner board. In the same way we might be able to add some of these changes an additional option. But we have to be careful when considering adding more products.

As far as the ALDL, It apparently transmits and receives at the 5 volt level. To transmit there is a 5 volt main voltage which is pulled down to 0.

So for this I believe if were to allow one of the 12 volt inputs and one of the 12 volt output sinks to be tied to pin 9 instead of the test port it would support ALDL without any other major changes.

That or supply a 5 volt tolerant line to pin 9. (Note some ODBI vehicles did come with ODBII style connectors. The connector in my '94 Caprice is the same as the ODBII connector)