You can plug the board into you PC and use a hyperterminal to manually “drive” the module as you learn how to use the AT commands. You just need a USB to RS232 adaptor cable. Learning and experimenting with the AT commands will be very difficult without this facility.
If your microcontroller has an RS232 port you can connect it directly to the RS232 port on the evaluation board. Otherwise the little voltage translator board that you have located looks perfect. You can access the 2.8volt UART signals form the edge connector on the evaluation board, pass them via the converter with 5 volt signals comming out.
Power supply requirements for the GM862 can be a little tricky. The evaluation board includes voltage regulation etc and just needs to be attached to a plug-pack.
Did you know that the GM862 contains a Python Script Engine (very C code like) and for many applications does not need to be connected to an external microcontroller?
You can plug the board into you PC and use a hyperterminal to manually “drive” the module as you learn how to use the AT commands. You just need a USB to RS232 adaptor cable. Learning and experimenting with the AT commands will be very difficult without this facility.
I spent some time with a GPS “Skypatrol tt8750” and “AT” commands and I are quite familiar. so I have no problem with the commands.
If your microcontroller has an RS232 port you can connect it directly to the RS232 port on the evaluation board. Otherwise the little voltage translator board that you have located looks perfect. You can access the 2.8volt UART signals form the edge connector on the evaluation board, pass them via the converter with 5 volt signals comming out.
is precisely what I need
a convert from 5v to 2.8v, but having no knowledge of electronics, I find it quite difficult to understand.
Did you know that the GM862 contains a Python Script Engine (very C code like) and for many applications does not need to be connected to an external microcontroller?
if the module “GM862” is pretty good for this reason.
I am a programmer PHP, python, perl. and for this reason that I bought.
My problem is I have to send other information from another sensor that comes from the “basic stamp 2.”
Combining these data with latitude and longitude and then sent to a server.
I was finding out enough about these issues and plenty of useful information:
- GM862 operates at 3.8v to 4.2v (power suply)
- Voltage levels on communication pins of uC are TTL 5V levels, on the Telit side are CMOS 2.7V (not even 3.3V).
- The Pines need 2.8V (RX, TX)
Therefore. How do I convert 5V (Basic Stamp 2) to 2.8v? Do any scheme foolproof?
Connect HV pin to 5volt supply, connect LV pin to 3.3volt supply, connect GND pins to both grounds on both supplies. Connect Telit RXD pin to RXI pin on converter, connect TXD pin on Telit to TXO on converter. Connect RXI pin on converter to the Tx pin on Stamp and connect Rx pin on Stamp to TXO on converter. I use the same converter between an Arduino and Telit GE865.
Wow did I screw that up…that’s what I get for typing too fast. Just so you’re aware the logic converter is capable of using 4 signals, you are only going to use 2 so you can pick either the top section (chan1) or the bottom section (chan2). The middle section is for your power supply connections. This is the correct pin out:
Connect HV pin to 5volt supply
connect LV pin to 3.3volt supply
connect GND pins to both grounds on both supplies.
Connect Telit RXD pin to TXI pin on converter, (LV side)
Connect Telit TXD pin to RXO pin on converter. (LV side)
Connect Stamp Tx pin to RXI pin on converter. (HV side)
Connect Stamp Rx pin to TXO pin on converter. (HV side)
It gets confusing because Telit labels their UART pins with respect to the receiving unit (Telit RX pin is actually an output and Tx is an input).
Even though you are powering it with 3.3volts the logic level output is actually between 2.7 - 2.8 volts.
It looks like your microcontroller board has an RS232 (9 pin connector) port so why not just connect that to the RS232 port on the GM862 board and do away with all that voltage translation.
Whatever voltage is used for the LV supply will be the level of your low-side signals, same for the HV supply and signals. In your last image, just connect the Chan1 TXO and RXI to the Parallax instead of looping them back to Chan2.
You only need to use one channel (two signals Rx and Tx) on a single logic level converter to make this work. Even though you are connecting a 3.3 volt supply as your LV the signal that goes into the Telit that you want to be 2.8 volts will in all actuality be about 2.5 volts well within the range of a logic one for the Telit. The HV to LV conversion on the converter is independent of the supply voltages used because the signal is dropped across a resistor divider using equal resistor values which means you’re output voltage will be half of your input voltage (5v / 2 = 2.5v) see the schematic…http://www.sparkfun.com/datasheets/Brea … er-v10.pdf
Just connect the wires from my previous post and you’ll be fine…as I said I’m using the converter between a Telit and Arduino and have monitored the signals with an oscilloscope and they are OK. Good luck.
I see the logic conversion question already answered but on other note want to mention I am completing very similar project (sending sensors readings to a php web site with gm862-gps module) and this topic viewtopic.php?f=13&t=20038&start=0 helped me to get the same kit for a half price from mikroelektronika.
Actually first I have bought the kit from sparkfun and when needed one more kit I have got it from mikroelectronika and they both works with the same program, just different board layout.
Just thought it could be useful to save you some money
Probably a dumb and very off topic question here but how do you guys make those diagrams with the pictures of the parts? Is that a program or? Thanks for any info on that.
http://www.ubuntu-pics.de/bild/74289/sc … Gtm64v.png
http://www.ubuntu-pics.de/bild/74294/sc … 3IuJ6r.png
but on other note want to mention I am completing very similar project (sending sensors readings to a php web site with gm862-gps module) and this topic