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[48X24X48X]

I probe pin 3 (timemark) of my EB-3531 and found that the output is always low. The chip is working properly in tracking. I need the PPS (timemark) output basically to put the host MCU into shutdown mode.

Any thoughts?

[GS_TECH01]

Just a couple of questions about this:

Can you please provide the serial number?
What is the date of purchase?
Where did you bought it from?
What is the firmware version? To determine this, please refer to the forum posting: http://www.usglobalsat.com/forum/index.php?topic=3514.msg8979#msg8979
Also, is the engine board able to get a good GPS fix?

[48X24X48X]

Here are my answers to your questions:

• Can you please provide the serial number? 11C25BE (underneath the bar code?)
• What is the date of purchase? October 2011
• Where did you bought it from? Szkaise
• What is the firmware version?
  
  • $PSRFTXT,Version:GSW3.5.0_3.5.00.00-SDK-3EP2.01 *46
  • $PSRFTXT,Version2:F-GPS-03-0907022*23
• Also, is the engine board able to get a good GPS fix? Yes, no problem on this and very reliable.

Please let me know if you need anything else.
Thank you.

[GS_TECH01]

One more question. Since you mention that the output is always low, what voltage value does it give you? At what range?

[48X24X48X]

The voltage is always 0V. And it stays there even with the satellite fix.

[48X24X48X]

May I know what is the maximum voltage that can be applied to the PPS pin? I know I'm not supposed to apply any voltage. But, I might have mistakenly configured the MCU IO direction and mistakenly applied 3.3V.

The PPS supposed to give 0-2.85V. Is there a maximum rating? I plan to place Zener diodes as protection, it'll be good if I know in hand the maximum voltage the pin can withstand. This is not specified in the user manual. Nearest Zener diode value would be 2.7V & 3.0V.

Thanks.

[GS_TECH01]

After checking with our engineers, they tested that this current firmware on the engine board did successfully output PPS. As 1PPS is a very small pulse (1uS) to be measured; thus, 0V is always indicated even with a 3D fix.
Without good oscilloscope and equipment, a user may miss the PPS output. That's why it's happening as you have stated. Since our firmware and hardware have confirmed that it supports PPS output, they suggested to adjust the oscilloscope.

Furthermore, they added that integrating Zener Diodes for protection would not help because 1uS pulse is too small. Also, it happens instantly. For that reason, you see that the voltage is always low.

[48X24X48X]

Hello,

That's why I'm not able to see the pulse! I did see blip of it. I thought PPS is a 1 second high & 1 second low kinda pulse. So sorry for the misconception. Let me measure once more and get back to you on this.

And may I know what is the maximum absolute rating that I can apply on the PPS pins (and also the TXA & RXA pins)?

Thank you for checking with the engineer.

[GS_TECH01]

According to our engineers, the maximum voltage rating that can be applied to PPS is 2.85V. As for the TX and RX pins, the maximum output voltage is 2.85V as well and the maximum input voltage is 3.6V.

Let me know if you have any questions.

[48X24X48X]

Thank you for the reply!

Measured the PPS signal before & after a translator chip and it works fine.
Will adjust the design to ensure all the EB-3531 pins are safe from over voltage.

Thanks again for the good support.

[GS_TECH01]

You're welcome. And, good to hear that it's working now!

Alright, just feel free to ask if you have any inquiries.