RealDash - Budget Digi-Dash For DTA

[SweetBadger 94]

Hi All, though I'd share some info on a mini project to build a budget digi-dash for the 205.

 

Currently have a DTA S40 ECU running throttle bodies on a GTi6 engine.

 

While sorting the wiring loom out for the latest race car I started thinking about the gauges / dash. We previously had aftermarket racetech gauges, but I always thought it looked messy with the std dash + aftermarket ones. So can't remember how but I stumbled upon a link to RealDash which is an Android/Windows/Iphone app that can connect to various ECUs DTA included.

 

After further investigation if you wire all the relevant sensors to the DTA ecu, then you can send the values directly to a phone / tablet running RealDash and you get datalogging, gps lap timing, gauges that you can customise, gear indicator (based on engine speed and gear ratio), warning lights that you can customise, and some really cool looking dash graphics!

 

I've added the following sensors:

 

- Oil temperature (Bosch blue one - same as coolant sensor - drilled and tapped the std oil temp hole to M16 and used an adapter back to M12 for the sensor), 1k pullup resistor required

- VSS - std Gti6 VSS, wired to ECU undriven wheel sensor input. Provides speedometer reading - you can use GPS on realdash, but not legal and no good in tunnels! Required a 4.7k pullup resistor on the signal wire. 8 pulses per rev. With speedo gearing set to 9 pulses per rev in DTA

- Oil Pressure Sensor https://ldperformance.co.uk/product/oil-fuel-pressure-sensor/

 

Then an RS 232 to bluetooth adaptor https://ldperformance.co.uk/product/bluetooth-adapter/

 

You have to enable Launch control on the DTA ECU to get the speed sensor working, and set-up the serial data feed, then set up the sensor scaling, but that's quite simple.

 

Once the Bluetooth adaptor is paired with the device and set up in Realdash (also very simple), you get the S40 data feed sent to realdash.

 

The only things you need to consider are the dash lamps for lights, indicators, handbrake, and the fuel gauge.

 

I bought a second hand Samsung Tab S 8.4 for £65 - this is Samsung's old flagship phone from 2014 and has a fantastic AMOLED screen the perfect size for the 205 dash  , and will fit where the clocks used to sit.

 

Total cost about £80 so far, and here's how it's looking:

 

 

 

Will be adding indicator lamps, Oil Pressure, Water Temp and Shift Light above the fuel gauge, and have a holder for the tablet which will be bolted to the dash panel.

 

 

 

Edited May 28, 2020 by SweetBadger

[SweetBadger 94]

Some more progress.

 

Dash wiring complete. Extra lamps for water / oil warning and shift light (x2), plus indicator lamps. 2 x diodes linked up to the stop lamp so that it comes on with either the water or oil lamps.

 

The oil warning lamp will be grounded by both the standard pressure switch on the engine, and the ECU (configured to switch at 25 psi when engine speed is over 3000 rpm)

 

Illumination for the fuel gauge was a total pita - eventually settled on an abs project box with 2 x standard dash lamps for illumination, and an internal compartment sectioned off for the fuel warning lamp.

 

Plastic holder for the tablet now mounted.

 

 

 

Had to trim the dash surround to make the opening larger, but you get a good view of the screen now

 

 

Only thing I'd change next time is to look at a digital aftermarket fuel gauge. Standard one was a pain to fit and means that the screen sits slightly off centre, which is surprisingly annoying when it's fitted to the car!

 

 

[opticaltrigger 52]

It's excellent Alex, really nice.

 

All the best,

O.T.

 

[Spesh 31 1 Cars]

Something like this is on my radar.

 

Did you sort the tablet to switch on when powered or do you need to manually put it on?

[Ron_Jaegers 10]

That looks really cool! I have a tablet in my 306 Estate talking to the ECU as well. It's quite nice although a bit laggy for my liking, how is that with the DTA and this software?

 

Would it be possible to wire the tank sender to the DTA as well and expose it as an additional analogue channel? Then the software could potentially pick it up as well. That would allow you to mount it dead-center again.

 

As for power to the tablet; I used a Nexus 7 with Timur's kernel (https://www.reddit.com/r/timurskernel/) that allows the tablet to go to deep sleep when the car is not running, and will wake it if it is. That allows for super quick boot times.

 

My tablet in the 306:

 

 

[Spesh 31 1 Cars]

I like that   What ecu is it talking to Ron?

 

[Ron_Jaegers 10]

It's a VEMS ECU, broadcasting an AIM data-stream.

[SweetBadger 94]

15 hours ago, Spesh said:

Something like this is on my radar.

 

Did you sort the tablet to switch on when powered or do you need to manually put it on?

 

The app has some power based global triggers, but nothing to switch on/off the tablet.

 

In my case, as the car won't get much road use I'm planning on removing the Tablet when not using the car - it just clips in and out of the holder.

 

On 6/12/2020 at 2:22 PM, opticaltrigger said:

It's excellent Alex, really nice.

 

All the best,

O.T.

 

Cheers, will be interesting to see how it performs in a hot race car. Suspect I may have to think about a small cooling fan on the back of it as I've had iphones doing satnav overheat on a hot day before now

 

4 hours ago, Ron_Jaegers said:

That looks really cool! I have a tablet in my 306 Estate talking to the ECU as well. It's quite nice although a bit laggy for my liking, how is that with the DTA and this software?

 

Would it be possible to wire the tank sender to the DTA as well and expose it as an additional analogue channel? Then the software could potentially pick it up as well. That would allow you to mount it dead-center again.

 

As for power to the tablet; I used a Nexus 7 with Timur's kernel (https://www.reddit.com/r/timurskernel/) that allows the tablet to go to deep sleep when the car is not running, and will wake it if it is. That allows for super quick boot times.

 

My tablet in the 306:

 

 

 

That looks great, slick interface, see what you mean about the lag though. The DTA data feed refreshes data points at 10Hz, I've not had the engine running with it yet, but have spun the speed sensor and moved the TPS it seems pretty responsive with very little lag. Will post a video up when I get it fired up.

 

There's one more analogue channel available on the DTA (analogue 3), which is assigned to fuel pressure. I could have probably repurposed this for fuel level and calibrated the DTA to the 205 sender, will see how I get on with it, and maybe that'll feature in the MK2 version (assuming my team mate doesn't crash the car again in the meantime!). Available data points from RS232 (more available from CAN bus, but not needed for my purposes):

 

RPM Throttle %

Water Temp C

Air Temp C

Manifold Pressure Kpa

Lambda (Unit Less)

Battery V (X10)

Undriven Wheel Speed Kph (x10)

Oil Pressure Kpa

Fuel Pressure Kpa

Oil Temperature C

 

 

 

[Ron_Jaegers 10]

8 minutes ago, SweetBadger said:

Cheers, will be interesting to see how it performs in a hot race car. Suspect I may have to think about a small cooling fan on the back of it as I've had iphones doing satnav overheat on a hot day before now

 

This could be an issue, yes. But it's mostly due to the battery/charger circuitry detecting a temperature that is too high to still charge the battery. With the Nexus 7 I have seen people remove the battery and wire it into the ignition switched +12v system of the car. That could be an option for you as well.

 

But nice mini-project overall!

Edited June 15, 2020 by Ron_Jaegers

[SweetBadger 94]

Thanks, will look at that if I have issues with overheating.

 

Engine is up and running, here’s a quick video of the dash. Seems nice and responsive, no real lag.

 

 

Using the “pole-position” dash skin. Very race-car! 

[SweetBadger 94]

Small update, the RS 232 to bluetooth adaptor from Ld Performance didn't last long   

 

Unplugged it to work on some ECU sensor settings and it was dead when I plugged it back in. Showing out of stock on their website, and I haven't been able to get a response from them about a repair / replacement.

 

So another way of connecting the Tablet to the ECU needed...

 

The Prolific USB to RS232 converter that I use with the laptop to connect to the ECU works with the Samsung Tablet no problem when plugged in through a USB OTG cable, it can even autoboot Realdash when it detects the Serial Converter being plugged in. The problem with this is that you can't charge the Tablet at the same time - the Tablet provides USB power to the device when it goes into 'USB OTG Host Mode'

 

There are 'charging' cables available, but they still don't do 'USB Host Charging' they only provide power to the USB device and not the Tablet.

 

There is a workaround however, you can fool the Tablet to thinking it is connected to a dock by putting the correct value resistance between the tablet's USB connector pin 4 (sense) and 5 (ground). In dock mode the Tablet will charge and work in OTG Host Mode.

 

 

The USB standard is 124k, but manufactures do not follow this and choose their own values.

 

124k didn't work, just charged the device

100k turned the cable in to a power transfer cable -> charge other devices from the phone, no good

 

Ended up trying a few values, and got lucky on 78K

 

So for a Samsung Tab S 8,4, using a 78K resistance between pin 4 and 5 (where the 100K resistor is shown above) = dock mode. The device will charge, and work in USB host mode. 

 

After chopping up a USB extension cable and 5 pin micro USB cable, then some soldering and heatshrink, I now have a charge / usb cable and RS232 converter with no bluetooth, so a direct wired connection between the Tablet and the ECU. Phew!

 

 

 

 

 

Edited August 3, 2020 by SweetBadger
Correction

[Spesh 31 1 Cars]

Good work.  Did it reduce any lag that you had too?

[SweetBadger 94]

I didn't find lag an issue with the bluetooth adaptor when it was working, but to be fair didn't have chance to test extensively.

 

Haven't had the engine running with the new cable, but can see throttle position changing and response is quick - as you'd expect really, there should be no lag caused by a direct serial -> USB connection.

 

I think any perceived lag will now be down to the 10Hz data refresh rate from the DTA ECU, which is a limitation of the ECU and would be the same for any digital dash using the ECU data stream.

 

Now just have to find some time to get up to the garage and finish off the rest of the car - not much left to do, but other things keep getting in the way at the mo!