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TDC7200: tdc7200 trigger pin issue

Part Number: TDC7200
Other Parts Discussed in Thread: TDC1000

Hi,

     i am working on water flow metering am using tdc7200 to find time of flight I am not able to see trigger signal on the trigger pin of TDC7200

i)How to configure the trigger duration...?

ii)please provide me a configuration for tdc7200...?

iii)How to generate trigger signal on tdc7200 chip..?

Regards,

Rashmi H M

  • Hello,

    You cannot configure the trigger duration. The trigger signal ends when the TDC7200 receives the first start signal.

    The default configuration is a good starting place for most ultrasonic measurement applications, and is designed to work seamlessly with the outputs generated by the TDC1000. If you provide more information about your application (level or flow, number of stops needed, general TOF duration, etc.) I can help with more specific settings.

    You generate a trigger signal by setting the start new measuremnt bit. Please see this section of the TDC7200 datasheet called "Measurement Sequence"

  • Hello scott,

                    thanks for the reply,

    i)am working on flow meter application

    ii)I need 3 or 5 stop pulses to be count

    iii)I don't have much idea about general TOF time If it is possible please let me what is General TOF..?

    iv)i have set the START_MEAS bit but then also am not getting trigger pulse..? Please suggest me configuration for flow measurement..? 

    v)i have made enable pin HIGH by connecting it to vdd.

    the connection i have done is same as schematic as shown below

    advance thanks,

    Rashmi HM

  • Hi Rashmi,

    Apologies for the delay.

    The general TOF is just a rough estimate of the expected time that you will be measuring with the TDC7200. If the time being measured is less than 500ns then use Mode 2, and if it is greater than 500ns use Mode 1. For basic evaluation to get up and running set the Clock counter STOP mask to 0 and the coarse and clock counter overflows to max so that no incoming STOP signal will be ignored and that the measurement period will last as long as possible.

    If the enable pin is connected to the same voltage source there could be problems. Once the device has power applied to VDD it needs to see a rising edge on the enable pin. If this happens at the same time that the device is powering up problems can arise. This may be why you are unable to set the start new measurement bit and see a trigger signal.

    I recommend connecting the enable pin to a GPIO on your microcontroller and pulling it high only when you intend to take a measurement. Also keep in mind there is a short time before the TDC7200 has stabilized after the enable is pulled high. It is recommended to wait 1.5ms before starting a measurement after enabling the device to allow the LDO to settle.

    Regards,