Question About PMB-648 GPS

NWCCTV

In this thread Ken Gracey recommended trying the C code for the new GPS on the PMB-648. However, the PMB-648 only uses the Yellow wire for Tx. The PAM-7Q uses both Rx and Tx. So, which wire on the PMB-648 is considered Rx? I only ask because in the tutorial for the PMB-648 it states to go by the wire color, not the markings on the device.

EDIT: I had my connections listed backwards.

Publison

I believe your answer is here:

http://learn.parallax.com/KickStart/28500

OK, it's not C Code, but shows the correct connections. I can verify it works with SPIN. Try the SPIN code first.

NWCCTV

That is what I was referring to. Only Tx is used. In the PAM-7Q code both Rx and Tx are used.

Publison

The TX is only used from the GPS module. There is no reason to use the RX unless you are transmitting commands to the GPS.

With the code in Post #2, you are only listening.

I am referring to the SPIN code. It only spits out data.

Phil Pilgrim (PhiPi)

Publison wrote:

The TX is only used from the GPS module. There is no reason to use the RX unless you are transmitting commands to the GPS.

True, but there is good reason to want to transmit commands to this particular module: mainly to disable static navigation. In this default mode, slow movements over small distances are not recognized. Here is a post that includes code to disable it.

http://forums.parallax.com/showthread.php/142775-PMB-648-Advanced-Questions?p=1130298&viewfull=1#post1130298

Here's another thread about the difficulty of transmitting to the PMB-648 and how I solved it:

http://forums.parallax.com/showthread.php/140908-Difficulty-transmitting-to-PMB-648-GPS

-Phil

Publison

I knew about those Phil, but I was trying to do baby steps with Andy first.

Those where going to be my next suggestion.

NWCCTV

@Publison, Thanks but I already completed the project you are referring to. I want to run the code Ken suggested and just need to verify which wire I use for the Tx since the code requires it's use.

NWCCTV

Not trying to use the code in Post# 2. Read OP. I want to do this in C using the NEW GPS module code.

Genetix

Andy, I think the RX pin is the blue wire because it's used for Constant Navigation with GPS on LEARN and the PMB-648 Product Specification shows the pin between TX and VCC is TTL RX.
http://learn.parallax.com/project/constant-navigation-gps/wire-emitter-follower-circuit
http://www.146.stampinclass.com/downloads/polstar-pmb-648-gps-product-specification

By the way the Kickstart diagram shows the last 2 wires are Green and Grey but product photos show Aqua/Light-Blue and White. What colors do you see?
http://www.abra-electronics.com/products/28500-Parallax-PMB%252d648-GPS-SiRF-Internal-Antenna.html

NWCCTV

I tried the Blue connected through the transistor but that did not work. The my wires are aqua and an almost very light grayish color, depending on the lighting.

Genetix

Have you tried it without the transistor?

NWCCTV

Not yet. I will give that a try on Saturday.

GordonMcComb

You ought to be able to trace out the proper wire using the edge connection diagram in the manufacturer's spec sheet, still available on the Parallax site:

http://www.parallax.com/sites/default/files/downloads/PMB-648-v0.1.pdf

I would assume any transistor in a similar circuit would be for inverting the signal, so I'd try it with and without. If you are trying this with the PMB-648 (the subject of your thread after all), be sure you use the TTL Rx, not the RS232 lines. Doesn't seem to be RS2432 on the new unit, but it does have I2C lines, which would equally provide no joy if using simple serial.

Looks like its time to update some of the Kickstarts...

Genetix

GordonMcComb wrote: »

Looks like its time to update some of the Kickstarts...

You're Kickstarts are great but some of them are showing their age. A legacy product section would be a very nice addition.

Phil Pilgrim (PhiPi)

The transistor in my circuit is only there for transmitting data to the GPS. You should not need one for receiving.

-Phil

NWCCTV

Phil, Is that the Blue wire? All I am trying to do is get this to work in C rather than Spin. I want to use it with my Wild Thumper and have pretty much got everything else working with C.

Genetix

Phil Pilgrim (PhiPi) wrote: »

The transistor in my circuit is only there for transmitting data to the GPS. You should not need one for receiving.

-Phil

What exactly is that transistor doing if you don't mind my asking?

PJAllen

P.E.
Pin 1 [yel] is data going out of the GPS (sentences)
Pin 2 [blu] is data going into the GPS (commands)

Phil Pilgrim (PhiPi)

Genetix wrote:

What exactly is that transistor doing if you don't mind my asking?

Read the post in the link I provided. It explains everything.

-Phil

Phil Pilgrim (PhiPi)

NWCCTV wrote:

Phil, Is that the Blue wire?

No, the yellow wire is for receiving data from the GPS.

-Phil

NWCCTV

@PJ Allen, That is what I was looking for. I will give it a try and see if it works or not and report back.