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I am currently working on redesigning a SirfIII based battery operated GPS logger. A MTK3339 based GPS module has been selected due to overall (advertised) performance.

The GPS logger uses a microcontroller to enable the GPS receiver in a periodic time interval, wait for a position and then turn off the receiver (leaving backup supply enabled that keeps the ephemeris data in RAM, allowing faster TTFF.)

After some testing the results show that the old SirfIII logger is still outperforming the new MTK3339 version.

Standby current of the new logger is only 1/4th of the old design.

Closer investigation showed now that the SirfIII GPS chip features a special mode called Sirfaware. This is resulting in 50-75% shorter position acquisition times compared to MTK3339.

Question:

  1. Is anyone using MTK based GPS modules and found a way to improve position acquisition or overall power consumption?
  2. Is the MTK3339 the right choice for a battery operated logging application?
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5 Answers 5

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I used a Mediatek GPS in a high-volume application, and this worked fine, but I did put a FET in the supply line to power the device down when not in use (keeping VBATT powered to maintain the ephemeris). This also allowed us to reboot the GPS if it went unresponsive in brown-out conditions.

With regard to comparing lock-in times, you need to be really sure this is a like-for-like comparison; the chipset vendors often claim 'magic sauce' that speeds up lock-in, but it is important to remember that the antenna and any RF circuitry also have a profound effect on this, and most importantly the presence of any RF interferers on the board, e.g. any harmonics of the CPU or switchmode PSU clocks.

A relatively small change to the board can have a profound effect on the time-to-fix, so with a new board, I used to monitor the difference in GPS output when the CPU is running or stopped, and likewise when the unit's switchmode PSU was running or not - also compare the results with the manufacturer's evaluation board, to see if my design was sub-optimal.

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I'm not exactly sure about MTK3339. But I recommend you to check out Neo 6M, Neo 7M and Neo 8M by Ublox. They are extremely efficient in term of power and very popular among hobbyists and in the industry as well. If you buy from AliExpress, you can get each module with an antenna for around $5.

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I'm not sure of the MTK3339 specs. Have you looked at other modules? uBlox makes small and power-efficient modules (e.g. MAX-8). Telit also makes modules.

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I don't have a lot of experience working with GPS modules (yet) but I know that the MTK3339 is used often in quadcopter design which runs off of a battery source. So it has proven to be applicable for battery operated logging applications, but I can't confirm that its the best choice.

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Added - 2023: This answer was deleted years ago due to the claim that it was plagiarised. There is now NO on-web record matching it. The URL does not appear in the "Wayback Machine".
The answer is useful, but unable to be atributed. RM.


The GPS logger uses a microcontroller to enable the GPS receiver in a periodic time interval, waits for a position and then turn off the receiver (leaving backup supply enabled that keeps the ephemeris data in RAM, allowing faster TTFF). After some testing the results show that the old SirfIII logger is still outperforming the new MTK3339 version. Standby current of the new logger is only 1/4th of the old design. Closer investigation showed now that the SirfIII GPS chip is featuring a special mode called Sirfaware. This is resulting in 50-75% shorter position acquisition times compared to MTK3339.

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