I did a bit of work last night and knocked up a simple 1" square circuit board layout for a throttle/gear switch interface:
One thing I've realised is that this small board could be multi-purpose:
- It has the ability to sense up to three analogue voltages (with ten bit resolution),
- Generate PPM or PWM signals that can either create an analogue voltage output or drive an RC controller with a stream of position pulses, like a servo tester
- Accept up to three digital inputs (at the expense of analogue inputs)
- Output up to three digital outputs (at the expense of other inputs)
- Send and receive RS232 serial data (via the programming port that can be used as another interface connection)
In normal use one analogue input will be used to measure the throttle voltage and the PWM pin will be used to generate the throttle output voltage that goes to the controller. One of the other input/outputs will be used as the gear change switch line and the last one will be used as the controller reverse line driver.
However, if you weren't using this as a retrodirect controller, you could use the same board, with some reprogramming of the Picaxe, to do other things, like act as an interface between a standard Hall throttle and an RC controller, or even provide throttle torque control instead of throttle speed control.
To implement torque control all that needs to be done is to hook up the shunt voltage sense connection on the controller to one of the analogue inputs and use this to give an actual torque feedback signal. The throttle voltage input would come from the throttle to the board and the Picaxe code would compare the demanded torque (from the throttle input voltage) to the delivered torque (from the shunt voltage) and output an appropriate throttle voltage to the controller. The result would be fairly good torque control, which many have said feels better than speed control.
There are probably other uses for this simple little board, limited only by the small number of I/O ports and the limited programme memory.
Jeremy