UV-40 GPS and Javelin Issues
Zaggy
Posts: 10
FYI, I am a Java programmer that is learning electronics and microcontrollers to help create products for my friend’s small business. My friend has a background in electronics, which he learned in the Navy. He is very busy right running the business, so get his time is hard. Therefore, I want to see if I can resolve this problem with help of this forum. Any advice, books or website would be wonderful.
Here is a little background on my project. I have a Javelin with a prototype board. In addition to the Javelin, I am using two LM317 voltage regulators, one at 3.3V for the UV-40 GPS unit and the other at 8.5V for a Max232. The project also uses an uM-FPU by Micromega. In addition, I have a magnetic compass and an EEPROM running on the I2C bus. I will be adding an I/O expander onto the I2C bus in the near future.
The problem I am having is the Javelin cannot read the pulses off the UV-40 GPS unit when directly connected. If I use the prototype board DB9 connection between the two, it works. Therefore, I purchased a few Max232’s to emulate the DB9 connection on the prototype board. I currently cannot get the Max232’s to work, I am wondering if the UV-40 is not creating enough voltage. I know the Max232 will not read any pulse below 3V. FYI, the UV-40 documentation states that it is TTL compatible. Currently, I have a set of simple tools that may not be appropriate to investigate this problem. Any help would be great.
Joe
Post Edited (Zaggy) : 1/23/2005 6:49:13 PM GMT
Here is a little background on my project. I have a Javelin with a prototype board. In addition to the Javelin, I am using two LM317 voltage regulators, one at 3.3V for the UV-40 GPS unit and the other at 8.5V for a Max232. The project also uses an uM-FPU by Micromega. In addition, I have a magnetic compass and an EEPROM running on the I2C bus. I will be adding an I/O expander onto the I2C bus in the near future.
The problem I am having is the Javelin cannot read the pulses off the UV-40 GPS unit when directly connected. If I use the prototype board DB9 connection between the two, it works. Therefore, I purchased a few Max232’s to emulate the DB9 connection on the prototype board. I currently cannot get the Max232’s to work, I am wondering if the UV-40 is not creating enough voltage. I know the Max232 will not read any pulse below 3V. FYI, the UV-40 documentation states that it is TTL compatible. Currently, I have a set of simple tools that may not be appropriate to investigate this problem. Any help would be great.
Joe
Post Edited (Zaggy) : 1/23/2005 6:49:13 PM GMT
Comments
If you don't already have them...download the datasheets for your MAX232.· I've used the MAX232CPE which only requires +5volts and 5extra caps to work.· So far as testing these (and you'll need the datasheet to see where the inputs/outputs are) if you just put +5volts on the TTLin port, then on the corresponding RS232 output, you should have a -12V.· And if you take off the +5V and ground that TTL input, then that -12V should change to a +12V.· (NOTE: +/-12Volts is the average RS232 voltage level swing...but anything more than +/-8volts would probably still work!.)
Obviously you'll need a voltmeter to view this...and assuming you do, then putting it on the output of your GPS unit will tell you if there's data coming out.· Now, if the data is moving fast enough, you're meter will only bounce around (data's too fast for the meter to actually 'read')!·
Are the grounds from the GPS and the Javeline connected?· You'll need them both at the same potentials to read the data line properly.
Start with the voltage readings and we'll move from there!
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Steve
http://members.rogers.com/steve.brady
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
Joe
MAX has a few flavours of their level converters.· You might have one of these other flavours; ie: needs a split 12V supply....
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Steve
http://members.rogers.com/steve.brady
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
That is what I was wishing for, but they are SN754410 Quad H-Bridge chips. These chips have the same pin count and hard to read. Thanks for your help!
Joe