Unable to configure TIMEPULSE pinout correctly

Q&A forumCategory: QuestionsUnable to configure TIMEPULSE pinout correctly
hrk1996 asked 2 months ago

I am attempting to read the TIMEPULSE of 100 ms (ON) and 900 ms (OFF) of the Ardusimple. I set the configurations on U center according to the ZED F9P integration manual, that is setting both the measurement rate (CFG-RATE-MEAS) and the time pulse frequency (CFG-TP-*) to 1Hz. However, when using PPS tools in Raspberry Pi to obtain the PPS information, I do not get any PPS signals, though I get them while using another GNSS receiver’s PPS pin. Also, when connecting the Ardusimple to a micro-controller digital input to see the obtained timepulse, no value is detected. On an Oscilloscope, the output wave from the Timepulse pin gives a very noisy wave. Any suggestions?  

Ardusimple Staff replied 2 months ago

Hi hrk1996, the default timepulse configuration is already 100ms ON, 900ms OFF, no need to change any configuration.
The LED “GPS FIX” is driven by this signal.
Can you confirm that by returning the system to default using UBX-CFG-CFG message you still have this behavior? Note that the signal is referenced to 3.3V.

hrk1996 replied 2 months ago

Hi, I was getting the ON and OFF states when using a logic analyzer, but it is only 0.6V maximum voltage in the ON state. Because of this, I thought it was just noise when using the oscilloscope. I have used Power + GPS (J1) plug to power the board, and the Timepulse pin 1 along with the ground pin next to the 5V_in pin. Is there anything wrong with my setup?

4 Answers
hrk1996 answered 2 months ago

Hi, I was getting the ON and OFF states when using a logic analyzer, but it is only 0.6V maximum voltage in the ON state. Because of this, I thought it was just noise when using the oscilloscope. I have used Power + GPS (J1) plug to power the board, and the Timepulse pin 1 along with the ground pin next to the 5V_in pin. Is there anything wrong with my setup?

Ardusimple Staff answered 2 months ago

HI hrk1996, I confirm it’s a limitation of the board that the timepulse works with +0.7V reference, instead of 3.3V as I mentioned above. Nevertheless the pulse should be very clean and easy to read. Hope you can continue your project with this limitation.

hrk1996 replied 2 months ago

Do you plan to correct this limitation of 0.7V to 3.3V in future releases? Asking since this will not be sufficient for my application and I will have to step it up.

Ardusimple Staff replied 2 months ago

Yes, will be corrected soon. We leave this question open and will inform you once it’s solved.

Ardusimple Staff answered 2 months ago

Yesterday we announced the new simpleRTK2B v1.1 that includes the improvement of timepulse with 3.3V. We close this question.

Ken McGuire answered 1 month ago

If you want to have a ~0-3.3V TimePulse output on the boards you already have, you can do one of two things. I did #1 on my boards.

  1. If you have surface mount rework skills, you can replace U1 (an NPN transistor) with a 2N7002 (logic level FET) That will give you the GPS Fix LED as well as ~0-3.3V TimePulse.
  2. you can cut the trace from the Timepulse pin to the base of U1. That is easy to do with an craft knife and a magnifying glass. However you will lose the GPS FIX LED functionality. (it may be on or off randomly as the base of U1 will be open.