Anyone with SLS & remote?

[Graeme]

Is there anyone with SLS and the remote who has a pwm-capable multimeter and might be prepared to measure a signal? I believe that I can build a low-cost module for D2 SLS owners to emulate the fob using a switch that could be mounted in the rear of the vehicle for easy access but I could do with a little information to speed the process. I don't have access to a D2 with SLS, let alone having a remote. Even a multimeter without pwm capability would help.

Whilst use of the fob requires that the facility be enabled in the BCU, I'm hoping that the SLABS ecu doesn't need enabling as I can only find reference to the BCU needing to be enabled. The BCU won't be involved in my proposed solution although the signal wire to the SLABS ecu from the BCU would be used.

[Banjo_pluker]

I thought that this was a factory only option

very keen to know how you go however

[Pedro_The_Swift]

more interest here too---

[SiddersC]

I have SLS and remote, but don't have acces to the multimeter

[dmdigital]

The BCU controls the fob encoding and the SLS light actuation but ultimately is in communication with the SLABS. The SLABS controls the compressor, height sensors, valves etc and is where SLS is activated.

If you can get something working I'm sure there's a lot of D2 owners who would be interested.

[Graeme]

The BCU passes the up or down indication in a fixed frequency 25 Hz pwm signal from the RF receiver to SLABS on a dedicated wire whilst a remote's button is pressed and the BCU's conditions are met. The up or down indication therefore has to be the use of different duty cycles, being the only other variable for a pwm signal.

Knowing whether it is a 5V or 12V based signal is necessary to be sure of avoiding damage to the SLABS ecu. The voltage can only be determined by observing the voltage whilst the remote is lowering or raising the vehicle. Testing using a 5V signal can't cause damage but may not produce any results. The voltage can be assumed from either using a digital volt meter and observing some instances of voltages above 5V whilst using the remote or from using an analogue volt meter and obvserving the maximum smoothed voltage during lowering or raising, as the maximum voltage should be well above 5V if the signal uses 12V. Note that the vehicle speed signal which is produced by the SLABS ecu is a 12V-based pwm signal, not that this is any indication that the lower/raise signal is also 12V.

Knowing the duty cycle of the individual up and down signals would avoid having to possibly do numerous trials using different duty cycles, although I have reasoned a starting point. A pwm-capable multimeter would show the duty cycle of the current signal.

A test module using 5V is ready to be sent for testing by the AULRO member who triggered my quest to provide a cheap alternative to the remote.

Edit: I've discovered that the 5V pwm output from the test module is recognised by my ACE speed signal modifier that inputs SLABS's 12V pwm speed signal. This indicates that supplying a 5V pwm signal in place of what's normally a 12V pwm signal from the BCU may be sufficient. Frequency and duty cycle are the pwm signal's main criteria when used for coded messages so I'm not particularly surprised.

[turps]

more interest here too---

me too. I would like it just so I can.

[lewy]

me to,will allow me to access the shed

[Graeme]

It may take a few weeks to work through the variables, finding test time and posting bits back and forth but within a month there may be something positive to report. I have 4 more options ready to test but will wait until the first test is done as any result may influence what will be tested next.

[lewy]

hows this progressing

[zzsteve]

Just some queries on this very interesting proposal:
Is the RF signal sent on the same key fob carrier frequency of 433 MHz ? If so, how does it avoid corrupting the BECM security (like parking outside the infamous Greenspot chemist/ Dick Smith store security systems).
Would it be easier to implement a separate transmitter FOB and matching receiver since we know the protocol thanks to Graeme?
Cheers,
Steve

[Graeme]

A test module was setup to try all duty cycles in 5% steps but it only caused slight shuffling movements of the suspension at 2 steps, indicating that the mechanism may work if the correct signal could be generated. A D2 owner with an oscilloscope has kindly monitored the RF receiver to BCU signal wire when the normal lock/unlock remote is used to gain insight into what the BCU to SLABS signal might be like. This has revealed that the signal is a high impedance 12V pulled low to create a coded pwm signal, not the other way round as I had assumed. The test module will be reworked to pull the signal low to create its signals rather than output a 5V or 12V pulse.

The RF receiver to BCU lock and unlock commands have a (rolling?) code component that the SLS remote would also have in order to confine the usage to a particular vehicle. The code segment does not conform to the stated 25 Hz pwm signal. The BCU likely removes the code segment from the message before sending it to SLABS but the commands may still not be simple pwm signals. The next test is a few weeks off yet but without a SLS remote to monitor, it will be the last unless a positive result is obtained.

[Graeme]

Is the RF signal sent on the same key fob carrier frequency of 433 MHz ?
Yes and its picked-up by the same RF receiver and sent to the BCU on the same wire and the BCU then sends SLS commands to SLABS (perhaps modified/simplified) if appropriate conditions are met. My idea was to send (wired from a module) appropriate signals directly to SLABS, bypassing the RF receiver and the BCU. If I can hit the jackpot then a cheap remote could be used instead of an on-off-on toggle switch.

[alpick]

Go Graeme!

[lewy]

thanks for the updates