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SDIO GPS: Globalsat 501
Posté le 26 août 2004 à 16:23:55 par gpspassion.

Globalsat SD-501 SDIO GPS

I would first like to clarify that the Globalsat SD-501 is not the first SDIO GPS, but the first SD generation released last year around the MEI design, did not offer a level of performance satisfactory enough to be considered functional in my opinion.

The SD-501 was first shown at CeBIT 2004 with a white casing. While other SD GPS receivers were on display (such as Royaltek, Holux), but the SD-501 was the only one with a dual folding antenna design that seemed fragile but Globalsat said at the time they were working on other ideas...Four months later, the SD-501 is available at Semsons under their i.Trek brand name and it's ready to be put to the test!

The SD501 certainly has an unexpected design that will be a bit of a surprise for most when opening the box. The SD501 in itself has a dual antenna that unfolds, and there is a "booster" that clips on to the extended part of the antenna with a connector that plugs into the side of that same antenna. It sounds complicated, but actually once you've put the various pieces together a few times, it's a "snap". Due to this unusual design, it's difficult to get meaningful measurements, but the pictures should give a good feel for its aspect and show how it compares to other designs. The main body weighs in at 26 grams and the booster at 8 grams. To conlude on this topic, there definitely is a sense of "fragility" and I wonder whether the tiny MMCX male connector will survive to too many connections, we'll see later that this should not be a problem anyway.

Installation, Compatibility and Target devices
Unlike Compact Flash GPS receivers or Bluetooth GPS receivers for that matter, the SD-501 requires the installation of a small (20kb) driver that will make the SD-501 appear on a "standard" virtual COM port. For some reason, a "trick" (see discussion thread) is required for my favorite "tweaking" software, Leadtek's CE Monitor, but otherwise it works "out of the box" with all other GPS software I have tried (too long to list here, but if you have specific software in mind, use this discussion thread) and as soon as te red LED blinks, indicating a fix, you're good to go!

The SD-501 will require a PDA with an SDIO port, which is the case of most current PocketPCs but not of older ones such as the Dell X5, the iPaq 1910 or the Audiovox Thera 2032 for instance. I successfully tested it with an iPaq 3970, a Toshiba E800BT and an iPaq 1710. Inserting it into my E200 (QTEK 8080) Smartphone caused it to reboot though!

The SD-501 will be of immediate interest to owners of single slot non-Bluetooth PDAs, and especially the 1930 that can't use a "mouse" GPS (except with a non portable IR cradle). For more comfort on single slot devices and to appeal to owners of dual slot devices (or single slot + BT) devices, there would have to be on-board memory (like on the Syson CF Memory GPS), but given the form factor constraints it looks like a challenge!

As implied in the introduction, the SD-501 performed well in my tests and proved to be fully functional for trouble-free use. This is no doubt due to the thought put by Globalsat into the sophisticated design, but also to the use of the high-sensitivity SiRFXtrac v2 firmware (see the Xtrac v2 "file" for details). Various levels of performance can be achieved by using the SD-501, folded, extended and with the booster snapped on (I did not notice any difference whether the booster was plugged in or not). While performance with the booster was the highest (130% on the GpsPasSion Sensitivy Scale compared to 150% for the latest XT2 Bluetooth GPS receivers), it remained at 100%+ without the booster. Folding back the antenna did reduce it quite a bit and the fix was lost on occasion.

Solid performance across the board, but as with other Xtrac v2 based receivers, while the high sensitivity works fine for driving, position updates will be irregular in pedestrian use unless you walk at a steady pace (XT2 appears to use a speed filter to stabilize the position).

Power Usage
I tested power usage with a Toshiba E800BT in various configurations (backlight, no backlight) with the stock (1,320mAh) and extended Mugen 2000mAh battery kindly provided by LionBattery. While the SD-501 is rated at 90mAh like the Haicom HI303MMF CF GPS, battery life with full backlight was 2h10 vs 2h40 for the HI303MMF. Interestingly the HI303S (XT2 too) also rated at 90mAh came in in between at 2h25. With the backlight off, battery life increased to 3h20. With the Mugen 2000mAh, battery life was a more useful 4+ hours (testing still ongoing) with backlight on.

As the SD-501 uses the Xtrac technology there aren't any "standard" settings (power saving, SBAS) you can modify as you could in ST mode, see here for more details. SiRF has recently made available some PocketPC Xtrac tweaking software (power mask, dop filtering, no speed filter adjustment though), but I haven't tested it yet and it's unlikely it will allow to improve on the optimized default settings.

With the SD-501, Globalsat have made sure they offered a (the first) fully functional SDIO GPS, first by using a sophisticated "multi-stage" design and second with the use of a the high sensitivity XT2 chipset, and this should be of great interest for owners of single slot PDAs, but the lack of on-board memory will limit its appeal to a broader range of devices. It's also competitively priced at $126* in the US at Semsons.

If you have questions or comments, you can use this discussion thread in the forums.

(*) These prices are valid at the time of writing on 08/29/2004 and factor in the Club GpsPasSion discounts.

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