Best thing to do is to calculate the voltages.
A quick recap on the Controller, The throttle is a 5K variable resistor (0 Ohms is Min throttle, 5K Max) This is connected in series with the LC resistor (8K2) & the Brake resistor (18k) LC & Brake resistors are shorted until the buttons are pressed, which then brings them into circuit.
The bottom of the chain is grounded and the top of the chain goes to an A-D converter in the Powerbase this is also connected to 5V through an 18K resistor on C7030. (3.3V on C7042) forming a potential divider.
So although the throttle is a variable resistor because one end of the resistor chain is grounded & the other end is connected to the supply through the 18K resistor, the A-D actually sees a voltage that will vary between 0V & 5V.
So now armed with this info you can calculate all the voltages. So a couple of exmples.
Throttle at Min, BK & LC not pressed. We will have 18K to 5V & 0 Ohms to ground, so A-D will see 0 Volts
Throttle at Max BK & LC not pressed. We will have 18K to 5V, 5K to ground, so A-D will see 5V / (18K + 5K) * 5K = 1.08 V
Throttle at Min BK not Pressed, LC pressed. We will have 18K to 5V 0 + 8K2 to ground, so A-D will see 5V / (18K + 0 + 8K2) * (0 + 8K2) = 1.56 V
Throttle at Max BK not Pressed, LC pressed. We will have 18K to 5V 5K + 8K2 to ground, so A-D will see 5V / (18K + 5K + 8K2) * (5K + 8K2) = 2.11 V
So best thing is to put together a spread sheet and calculate them all.
As can be seen although quite simple externally the software in the Powerbase microcontroller has to do some clever maths because the range & resolution of the throttle voltages change dependant on which buttons are pressed. In the above examples with no buttons pressed Min to Max throttle is 0V to 1.08V. However with LC pressed Min to Max becomes 1.56V to 2.11V.
All the above is for C7030, for C7042 you need to change 5V to 3.3V which is why SCP-1d which
sends out a voltage simulating the effect of the potential divider does not work and you need a SCP-1d 3.3V.
If you want your controller to also function with the SCP-1d easiest way is to copy the Powerbase input circuitry with the 18K to 5V, controller resistance chain to ground, then if your box works with a Scalextric controller it will also work with SCP-1d. If you also want it to work with SCP-1d 3v3 you will have to do some clever stuff in the firmware to correct for the reduced voltage range. If you have a "resistive" output at the Powerbase end then that should be fine for both C7030 & C7042.
Rich
