Has anyone tried using the ultimate gps module on a standard pc serial port?
All I get from minicom is a bunch of jibberish
I have verified the serial config in minicom - 9600 8n1 no flow control
ultimate gps and pc serial port
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- tastewar
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Re: ultimate gps and pc serial port
I know all the doc says 9600 and that seems to be standard now for gps, but have you tried any other rates? 4800 was standard for gps for a long time; I've seen 19200...
- bilsch
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Re: ultimate gps and pc serial port
I did try other rates out of curiosity however i know for sure it is 9600
With the ftdi adapter 9600 8n1 works but I want to use the hardware serial port on a linux x86_64 box
Out of curiosity I tried another usb to serial adapter ( olllld adapter :-> ) I get the same thing - just a bunch of jibberish
With the ftdi adapter 9600 8n1 works but I want to use the hardware serial port on a linux x86_64 box
Out of curiosity I tried another usb to serial adapter ( olllld adapter :-> ) I get the same thing - just a bunch of jibberish
- bilsch
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- Joined: Thu Oct 25, 2012 5:16 pm
Re: ultimate gps and pc serial port
I'm not sure if using a multimeter will be accurate enough but thought it worth a shot.
So, when I hook the positive end of my multimeter to the tx out from the gps I see it get to around 3 volts. Is it possible the hardware serial adapter is giving me garbage because the signal voltage is too low?
http://en.wikipedia.org/wiki/RS-232#Voltage_levels
So, when I hook the positive end of my multimeter to the tx out from the gps I see it get to around 3 volts. Is it possible the hardware serial adapter is giving me garbage because the signal voltage is too low?
http://en.wikipedia.org/wiki/RS-232#Voltage_levels
Valid signals are either in the range of +3 to +15 volts or the range -3 to -15 volts; the range between -3 to +3 volts is not a valid RS-232 level
- tastewar
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Re: ultimate gps and pc serial port
Sounds quite plausible. There's a link to a little board that would help in this thread:
http://forums.adafruit.com/viewtopic.php?f=10&t=32437
http://forums.adafruit.com/viewtopic.php?f=10&t=32437
- adafruit_support_bill
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Re: ultimate gps and pc serial port
Yes a TTL to serial adapter is needed for interfacing with an RS232 serial port. The signal voltages on RS232 can cause damage to the GPS module.
- bilsch
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Re: ultimate gps and pc serial port
What is the voltage of the gps module and what voltage is a pc serial port? Assuming the voltage off of rs232 serial port is higher than the gps module I suppose I could try to limit the voltage?Yes a TTL to serial adapter is needed for interfacing with an RS232 serial port. The signal voltages on RS232 can cause damage to the GPS module.
- tastewar
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Re: ultimate gps and pc serial port
But you have to boost the voltage in the other direction. There's a whole family of chips (e.g. MAX232) that bi-directionally convert between TTL level voltages and RS-232 levels. That little board I linked to (here it is again: http://www.suntekstore.com/goods-140026 ... oard_.html) has the support circuitry built-in, which is nice, but it's a crappy little thing otherwise. I went through 3 of them trying to solder wires to the little pads, and having the pads lift off the board :-/
Hence my asking if Adafruit would consider producing a similar product. Cause their stuff rocks.
Hence my asking if Adafruit would consider producing a similar product. Cause their stuff rocks.
- bilsch
- Posts: 17
- Joined: Thu Oct 25, 2012 5:16 pm
Re: ultimate gps and pc serial port
tastewar,
I completely missed your previous posting thanks I'll see if I can dig one of those up!
I completely missed your previous posting thanks I'll see if I can dig one of those up!
- bilsch
- Posts: 17
- Joined: Thu Oct 25, 2012 5:16 pm
Re: ultimate gps and pc serial port
tastewar,
That maxim chip would very likely resolve the rx/tx side of the equation ( my only stated need in this thread ) but since this is for a gps unit I plan to also use pps as a part of the time sync for additional accuracy.
Oddly, with pps connected to the cts pin on the ftdi board I don't actually get the pulse registered in the kernel pps driver. I'm going to try out the gpio approach on my pi but my C foo is ... well, very very limited so far. i had posted on this previously and no one responded :-< ( http://forums.adafruit.com/viewtopic.ph ... i+gpio+pps )
Thanks for the hint about the maxim chip!
That maxim chip would very likely resolve the rx/tx side of the equation ( my only stated need in this thread ) but since this is for a gps unit I plan to also use pps as a part of the time sync for additional accuracy.
Oddly, with pps connected to the cts pin on the ftdi board I don't actually get the pulse registered in the kernel pps driver. I'm going to try out the gpio approach on my pi but my C foo is ... well, very very limited so far. i had posted on this previously and no one responded :-< ( http://forums.adafruit.com/viewtopic.ph ... i+gpio+pps )
Thanks for the hint about the maxim chip!
- tastewar
- Posts: 408
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Re: ultimate gps and pc serial port
I wonder if this tutorial, that I bookmarked earlier for myself, would help. It talks about using the GPIO serial port. Definitely avoids the need for level shifting!
http://learn.adafruit.com/adafruit-ulti ... ead-of-usb
http://learn.adafruit.com/adafruit-ulti ... ead-of-usb
- bilsch
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- Joined: Thu Oct 25, 2012 5:16 pm
Re: ultimate gps and pc serial port
Yes, that does work though note they are not touching the pps side of the equasion.I wonder if this tutorial, that I bookmarked earlier for myself, would help. It talks about using the GPIO serial port. Definitely avoids the need for level shifting!
Here are the links I'm looking over:
http://www.raspberrypi.org/phpBB3/viewt ... 8&p=129224
http://www.raspberrypi.org/phpBB3/viewt ... 06#p142606
It seems as though others have had the same idea re using the pi and gpio for the pps ( and hardware serial uart for comms ).
Curious this has not been merged in to the raspberry pi kernel yet. Guess if I can get it working I'll send a pull request.
-
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Re: ultimate gps and pc serial port
I have the same problem: I need to attach this GPS to a serial port on a PC to sync the clock, it means I need to use the PPS output. Wouldn't this converter work? http://www.adafruit.com/products/395
I just found RS232 to TTL with 4 pins (RX, TX, VCC, GND). How can I use the PPS pin with serial port (RS232)?
I just found RS232 to TTL with 4 pins (RX, TX, VCC, GND). How can I use the PPS pin with serial port (RS232)?
- adafruit_support_mike
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Re: ultimate gps and pc serial port
Stepping back for a second, how will the PC recognize the pulse once you have the wiring right?
-
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Re: ultimate gps and pc serial port
I imagine it would work the same way that others GPS work: connecting PPS pulse to pin 1 RS232. No?
adafruit_support_mike wrote:Stepping back for a second, how will the PC recognize the pulse once you have the wiring right?
Please be positive and constructive with your questions and comments.