What?
A plug'n'play adaptor to let Dave desk-test the MegaTunix code for VEMS.
Why?
Dave A needs a working Genboard to test with. This means he needs a way to fake signals and check the values. He has a MS Stimulator, so an adaptor to Genboard is a quick and an easy way to provide this.
How?
DB37M to EC36F cable:
- 30 cm long
- Heatshrink cover
- Tested
Firmware:
- Known good firmware release
Config:
- 2 injector channels
- PWM idle control
- Fuel pump output
- No ignition channels
- 12V distributor style trigger
- Coolant temperature sensor
- Throttle position sensor
- Inlet air temp sensor
- 1 narrow band lambda channel
Pinout
Pins 1 to 19 on the first row of the DB37 connector on the MegaSquirt board are grounds (not important here but pin 19 is supposed to be a special sensor ground but no distinction is made on the v2.2 PCB). On the Stimulator board pins 7 to 11 are used as grounds so these are the ones to tie together with grounds on the Genboard: Power ground pins 5, 21, 32 and "regular ground" pin 26.
Oxygen sensor input
could be connected to one of the analog inputs of the MCP3208 (?). Possible, but non-standard... It's unfortunate that we're using EC18 as well, but std config appears to be through Nernst Channel 2 / EC18-1.
I think it makes more sense to prepare for testing WBO2 channel, since NBO2 is very rare nowadays. (also: WBO2 testing equipment helps to find out if the same channel works for NBO2).
Proposal for (sensorless test-) setup:
- variable resistor (270..470Ohm) between pump+ and nernst
- 330..470 Ohm 1.5W between heater- and heater+
- 470..2200 Ohm NTC between nernst and pump- (2x2k2 NTC in parallel is also fine). Make this touch (eg. wrapped together) above heater resistor
If you get the parameters right, this setup can make a stable (wb)o2 signal on LCD and MegaTunix. The necessary condition is that both Ri (AC level on nernst) and nernstdc (appr 4.45V DC on nernst) can be kept on target by the controller.
| DB37 | EC36 | Function | Comment |
| 1 | Ground | ||
| 2 | Ground | ||
| 3 | Ground | ||
| 19 | Sensor Ground/Return | ||
| 20 | 2 | MAT | |
| 21 | 14 | CLT | |
| 22 | 1 | TPS | |
| 23 | - | O2 | EC18 Pin 1. See GenBoard/Manual/Config/NBoxygen |
| 24 | 27 | Coil (Tach) | Primary trigger |
| 25 | X11 Jumper | ||
| 26 | 28 | Vref | +5V (to sensors) |
| 27 | X12 Jumper | ||
| 28 | 25 | +12V Power to ECU | |
| 29 | X13 Jumper | ||
| 30 | 3 | Fast Idle | |
| 31 | X14 Jumper | ||
| 32 | 7 | Injector Drive #1 | Injector channel A |
| 33 | 7 | Injector Drive #1 | (not really required) |
| 34 | 19 | Injector Drive #2 | Injector channel B |
| 35 | 19 | Injector Drive #2 | (not really required) |
| 36 | N/C | ||
| 37 | 15 | Fuel Pump |
An idea ?
Would it be possible (within a certain time and money frame) to create a GenboardStimulator with the following features:
- Variable frequency output
- Variable voltage output
- Outputs are controlled via software, not POTs
- Ability to read output signals from GenBoard
- Various signal/waveform generators
A couple of uses:
- System Test. Hook it up and run through the various tests to see that firmware responds in a predictive way.
- Hardware Test. Hook it up and take all the soldered hardware for a spin. Perhaps the GenBoard will only short-circuit if certain components are swiched at the same time?
- Configuration Test. User has problems with his configuration, load it up and see what happens.
- and lots of others.
I guess it's not impossible to create; but how much would it cost? Money and time-wise?
Component suggestions:
- http://pdfserv.maxim-ic.com/en/ds/DS1844.pdf digital pot
Spec for the planned smart-stim
Even though work on this is started, i won't drop the idea of a mot-ms stimulator adapter harness..
- Trigger outputs
- Primary trigger, representing engine speeds up to 10000 rpm
- Support for distributor pulse-per-ign signal
- Support for 24-1, 36-1 and 60-2 wheel signals
- Secondary trigger - synced to primary trigger
- Support for #1 @ TDC cam trigger
- Primary trigger, representing engine speeds up to 10000 rpm
- 28 digital inputs
- 8x INJFET
- 8x IGN_IGBT
- 4x misc drivers
- Fuel pump
- Fast idle
- 4x stepper outputs (push/pull type)
- 2x misc high current drivers
- Analog outputs
- CLT (grounding)
- MAT (grounding)
- TPS (resistive, or maybe 0-5Vout)
- Fuel pressure (Vout or grounding, maybe with jumper to choose)
- Exhaust backpressure (same as for Fuel Pressure)
- Exhaust temperature
- 2 Lambda ouputs. Switchable between 0-1v NB input and WBO2 simulation.
- Knock signal
- Digital outputs
- Momentary buttons?
- Toggle switches?
- LED's
- 28 LED's for each digital input
- 4 extra, could always be useful
- LED or LCD display for output settings
WBO2 can be tested as documented at top of page by mcell.
The minimalistic VemsFrontier/MiracleBoard would provide more than the stims that are used today - definitely not several dozen inputs and outputs (if that's needed, use a v3 :-)
Today, most people just use ElectronicDesign/TriggerSignalGenerator or OutputTrigger to test board. Very simple and effective.