[Ovmsdev] HUD Cables

[Mark Webb-Johnson]

> had to remove his OVMS because he
> had installed a dashcam and needed to plug into the diagnostic
> connector to get +12V.

I suggest he “T" it. If he can wire up a plug for that weird Roadster DIAG port, he can wire up a socket as well. :-)

There are plenty of places in the roadster to tap into permanent 12v, but great care needs to be taken because drawing too much power constantly can trigger the switchpack to keep APS fully on all the time. People putting in audio head units commonly hit this issue.

> Does the +12V Vehicle Power just come straight through from the
> diagnostic port connection?

No. It goes through a switched output so we can turn it on/off under program control. That might be useful to him. He could remotely turn on/off the dashcam power feed. OVMS v3 can also be configured to just switch it on automatically on boot.

Regards, Mark.

> On 23 May 2018, at 2:55 PM, Stephen Casner <casner at acm.org> wrote:
> 
> On the Roadster drive organized by spiderguy this past weekend, one of
> the participants mentioned that he had to remove his OVMS because he
> had installed a dashcam and needed to plug into the diagnostic
> connector to get +12V.  I told him that OVMS v3 will have the ability
> to present an OBDII connector, which is what the camera really wants.
> 
> Does the +12V Vehicle Power just come straight through from the
> diagnostic port connection?
> 
>                                                        -- Steve
> 
> On Wed, 23 May 2018, Mark Webb-Johnson wrote:
> 
>> 
>> As discussed, the HUD cables have been produced and seem ok. I received a pair today, hot off the production line in China. Here is the specification:
>> 
>> OVMS v3 HUD/OBDII-F Cable
>> 
>> One end (DA26-M) connects to the OVMS v3 DIAG (expansion) connector. The other end provides an OBDII female (J1962-F) connector. Cable wiring is as follows:
>> 
>> J1962-F   DA26-M  Signal
>> 4         8       Chassis/Power GND
>> 5         8       Chassis/Power GND
>> 6         16      CAN-H (primary CAN)
>> 14        6       CAN-L (primary CAN)
>> 16        18      +12V Vehicle Power
>> Cable includes a 120ohm resistor between DA26 pins 16 and 6.
>> 
>> This provides for an OBDII expansion port for OVMS v3 and allows devices such as OBDII dongles, Heads-up-Displays (HUDs), etc, to be connected to OVMS using the ‘obd2ecu’ firmware module.
>> 
>> They look really nice. Moulded, tough, and stubby. DA26 expansion connector to OVMS has screws to hold it in place, and they seem to work well. We had to make a MOQ (minimum order quantity) of 100, and they will go up on Fasttech over the next couple of days (along with stock replenishment for some other cables running low / out of stock). These are relatively expensive to make (moulded DA26 connectors, 120ohm resistor, etc), so will be US$14.50 each (including free shipping).
>> 
>> Regards, Mark.
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