Technical Queries

Dear all,

I hope you're having a good week so far, and happy new year!

I hope it's alright, but I do have a couple of questions:

1. In the sensor board manual CN2 is described as being able to isolate the U9 start bar detection, so that pin 9 for CN1 only reads U8 (or at least from my understanding), could any further information regarding how to use CN2 (such as information relating to R9, R10 and LED17 or schematics) be provided or should this be ignored since it isn't covered in the newer version of the sensor board manual?
2. What does shorting the different pins on JP1 from the motor driver board actually do? The manual states it switches PWM output terminal and direction selection terminal-but from what, and to what?

Thank you for your help so far, and I look forward to your reply.

Kind regards,


  • Hi Miranda,

    In answer to your first question, please refer to section 2.9 Principles of Sensor Circuit in the Sensor Board Assembly Manual. U9 (the S6846) is basically the same device as U1-8 (S7136), the only difference is the physical package as U9 is mounted facing forward towards a start bar instead of down at the track.

    With this in mind the theory behind the circuitry for U1 can be applied to the circuitry surrounding U9 (so the R10 pull up resistor is in place of RA1, R9 instead of R1 etc.)

    The major difference in the circuitry is the inclusion of CN2, JP1 and the fact that the signal BIT0 is shared for both U8 and U9. Section 2.8 details the relationship between the start bar detection sensor U9 and the sensor U8.

    As we can see in the section 2.2 Circuit Diagram, JP1 is a jumper link which is connected using a track by default. If this track were cut U8 and U9 would be separated; U8 would function the same as U1 to U7 and U9 would function similarly with the caveat that it would no longer have a direct connection off board (as it no longer connects to BIT0). CN2 allows us access to the sensors Vout pin, VCC and GND. Using the logic described in section 2.9 the effects of shorting Vout to either GND or VCC can be determined.

    In answer to your second question JP1 is used to swap the PWM signal with the direction selection signal for the left motor as you mentioned. See section 2.2 Circuit Diagram which shows how the wiring is affected by this swap.

    I believe this was implemented to allow the Motor Drive Board to connect to different MCU boards. The board currently being supplied with the kits is the RX62G which uses the default wiring (same as the RY_R8C38). Another board option that has been used in the past is the RY3048 in which the signals from the MCU were swapped (likely due to pin config settings). To sum up, with JP1 left in its default configuration as per the latest Motor Drive Board Manual the two signals should be connected through to the correct places from the MCU to the Motor Drive Board.

    I hope this helps,