Anyone have the schematics handy?

I have mislaid my NHW11 schematics and hopefully someone out there might help check two signal sources. The idea is to see if I might put an MSP430 inline with the speed signals that feed the 'Multi Display' and 'Combination Meter.' Both have pulse signals that are used to generate the speed and MPG:

• Combination Meter - connector A, pin 9, 0-14V, speed encoder pulses
• Multi Display - SPD, connector M5, pin 5, 1-9V, "Fuel efficiency cannot be calculated"

I suspect both signals come from the ABS ECU because it receives the wheel encoder signals and generates at least four pulse signals. It would make sense that the ABS ECU generates the speed pulses needed by the two displays.

I'll probably find the manual in a day or so but wanted to ask if anyone can check their copy to identify the source.

The reason for a 'spoof' circuit is I am running tires that are 107.2% larger than stock. Right now, I'm using a Garmin nuvi as a GPS speedometer. But I would also like to have the 'Multi Display' show the accurate MPG without having to use a calibration factor.

LATE:

I checked the ZVW30 schematics and it looks like the combination meter is the fan-out for the velocity signal from the 'skid control' (i.e., ABS controller). It passes through a single connector making inserstion much easier. My thinking is the NHW11 ABS controller may have the fan-out built in. If so, it will take two MSP430s to 'spoof' the velocity signal.

Thanks,
Bob Wilson

 

PERFECT!!!

It is the same architecture as the 2010. I'm not sure about the color code but this meets my requirement very nicely!

For the MFD, I'll tap GND, B+ (with a PTC fuse,) and intercept the pulse signal feeding pin 9. These will go to an RJ-45 female socket installed at the base of the center console, high over the carpet. In stock operation, an RJ-45 plug will jumper the pulse signal to the MFD. But it will also provide jumper points to measure the pulse timing as a function of indicated speed.

I'll then put together an MSP430 with a linear regulator to 3.3V, xtal clock, resistor divider network on the pulse-in, and an NPN transistor to pull-down the pulse-out feeding the MFD with a pull-up resistor from the B+. There will also be a way to adjust the calibration offset.

​

Texas Instruments MSP430 microcontroller from an EZ-MSP430
- automotive grade part
- 16MHZ at 3.3V, <2 ma.
- 256B RAM
- 4096B FLASH, multiple banks
- 10 I/O pins

P0/1 - LED driver on daughter board
P0/2-8 - digital I/O and/or ADC input
P1/1-2 - watch xtal for precise timing​

OPERATIONAL SCENARIO [DRAFT]

Multi-Function Display

The pulse-in, slope interval will be measured on each transition. This will be multiplied by the calibration offset to adjust a pulse-out, signal switching the NPN transistor state. Changes to the clock driving the NPN transistor will occur only when the output timer expires . . . or at very, slow speeds (i.e., stopped) . . . off. Changing the clock interval will preserve the next, expected level.

By default, the initial calibration constant will be 100%, no offset. Holding an "UP" button, must be added, will increase the calibration offset by 0.1%, 0.2%, 0.5%, 1.0%, 2.0%, 5.0% with a LED flash at each level. Holding the "DOWN" button, another part, will decrease the calibration offset by 0.1%, 0.2%, 0.5%, 1.0%, 2.0%, 5.0%. This will stay in RAM until 15 minutes after the last button press have passed when it will be written to a FLASH bank, over-writing the initial 100% offset.

Alternatively, I may mount a trimmer resistor and read out the value with the A/D converter. In effect, the trimmer becomes the initial calibration offset. The LED can flash the calibration value in Morse code. I like this approach, KISS.

Combination Meter

This will be left 'as is' but the housing will have a mounting slot for a Garmin nuvi used as a GPS speedometer. This will provide a GPS based distance that can be compared with the tripmeter values. Being able to compare the GPS trip distance and the combination meter trip meter distance means we will have an accurate, independent measure of the calibration offset.

Meanwhile, the speed will be GPS measured and by default, nuvi recorded. The GPS specific power cable will be embedded in the instrument panel.


Thought? Comments?

NOTE: Extreme calibration constants, say 200%, could lead the MFD showing impossibly high MPG. But what fun is there in that! I am more interested in getting an accurate reading of the true MPG.

Bob Wilson