Editing PG31 GPS USB Dev Board
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[[Image:Main-Eval-PG31-USB-Loaded.jpg|PG31 USB Dev Board]] | [[Image:Main-Eval-PG31-USB-Loaded.jpg|PG31 USB Dev Board]] | ||
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− | <b>Description:</b><br> You've probably heard about the CP210x USB ICs from Silicon Labs, now here's an application that uses it. The CP2102 gives us 3V TTL to a VCP (virtual comm port) over USB as well as generating the 3.3V needed for the board. | + | |
+ | <b>Description:</b><br> You've probably heard about the CP210x USB ICs from Silicon Labs, now here's an application | ||
+ | 1000 | ||
+ | that uses it. The CP2102 gives us 3V TTL to a VCP (virtual comm port) over USB as well as generating the 3.3V needed for the board. | ||
In this project we demonstrate how to: | In this project we demonstrate how to: | ||
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[[Image:PG31-USB-Connection.jpg|PG31 USB Connection]] | [[Image:PG31-USB-Connection.jpg|PG31 USB Connection]] | ||
− | The USB connector has four pins : Vcc (*around* 5V), GND, D | + | The USB connector has four pins : Vcc (*around* 5V), GND, D , D-. Tying these four connections to the CP2102 is easy enough. |
[[Image:PG31-USB-Connection-Schematic.jpg]] | [[Image:PG31-USB-Connection-Schematic.jpg]] | ||
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If you're playing with GPS, you've ''got to have a battery backup''. The 12mm coin cell lithium allows the PG31 (and many other GPS receivers) to retain the alamanac data. This small battery provides just enough juice for 3-5 years. By having alamanac data at power on, the GPS receiver will be able to do a warm lock instead of a cold lock. Cold locks take 1-2 minutes, warm locks, as little as 30 seconds. The alamanac data, in effect, allows the GPS receiver to 'guess' where it is in the world ("Last time I was on I was in Ohio, therefor, I will assume I'm near there"). | If you're playing with GPS, you've ''got to have a battery backup''. The 12mm coin cell lithium allows the PG31 (and many other GPS receivers) to retain the alamanac data. This small battery provides just enough juice for 3-5 years. By having alamanac data at power on, the GPS receiver will be able to do a warm lock instead of a cold lock. Cold locks take 1-2 minutes, warm locks, as little as 30 seconds. The alamanac data, in effect, allows the GPS receiver to 'guess' where it is in the world ("Last time I was on I was in Ohio, therefor, I will assume I'm near there"). | ||
− | If you're unfamiliar with Lithium Coin Cells - they come in a couple different sizes. I prefer 12mm just cause it's small but beefy enough to do most of the BBR (battery backed ram) that we need to support. The battery itself has a postive top (noted by the plus) and a ground on the bottom. You normally create a pad on the PCB for the ground and the coin cell holder is | + | If you're unfamiliar with Lithium Coin Cells - they come in a couple different sizes. I prefer 12mm just cause it's small but beefy enough to do most of the BBR (battery backed ram) that we need to support. The battery itself has a postive top (noted by the plus) and a ground on the bottom. You normally create a pad on the PCB for the ground and the coin cell holder is p |
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+ | ositive. We've learned the hard way that the bottom part of the cell is sometimes concave. This means that when you slide the coin cell onto the board, the concave ground part of the cell may not contact the PCB pad very well. If you're using a paste stencil, just leave a cutout for this pad. The extra paste will add 5-10 mils of solder to the pad. If you're solder the thing by hand, add a little blob of solder to this ground pad to give it some height. When you insert the battery, it should ride nicely on top of the ground pad blob. | ||
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===PG31 Footprint=== | ===PG31 Footprint=== |