[SOLVED] emulating a switch close

[Willykilly]

Hi,

I am working on a GPS logger. I am using Sim 18 module. This module by default boots up in sleep mode. To wake this gps receiver up (only then it sends the gps info) I have to close a switch. The switch is like a keyboard switch. After I release the press , the switch comes back to position(like a reset switch). What is done is a logic high is momentarily applied as long as switch is pressed and the gps receiver comes to wake mode. I tried to send a logic high signal from a micro to wake up the gps.
But it is not working . I verified with a scope if logic high is available on the micro's pin. Any ideas...

Thanks.

 

[bigdogguru]

Also have you implemented a pullup or pulldown resistor on the appropriate pin?

If it is not working with a momentary switch. Have you debounced your momentary switch?


If you could post a schematic of the circuit, it would be helpful.

---------- Post added at 19:34 ---------- Previous post was at 18:44 ----------

After further research.

Reference SIM18 Hardware Design Guide, pg 18, Section 3.2.4 ON_OFF





The pulse to switch modes must be greater than 90us and less than a second.

Apparently, you alternatively could use a command to shutdown the SIM18:

Reference SIM18 NMEA Message Specification Guide, pg 26, Section 2.3.10 Message ID 117: Systems Turn Off





Hope the info helps,

BigDog

 

[Willykilly]

Hi,

I am using this GPS module. https://m2m-com.com/media/files/SIM18_EVB_kit_User_Guide_V1.00.pdf.

I used PIC 16f 877a micro. The gps module works with a momentary switch. But it is not working if I sent a logic high to the switch connections. I will try the pull up resistor suggestion. Where to put the pull up resistor, I guess the micro is already having a pull up on the port pins.

Thanks.

---------- Post added at 19:53 ---------- Previous post was at 19:48 ----------

Hi,
Thanks for your message. I am reading the page 26 and I am basically trying to switch it on from its default sleep mode. I thank you, you have given more information.

 

[bigdogguru]

Are you using the SIM18 Eval Board or just the module? I examined the schematics to the eval board and the required pullups/pulldowns are already implemented on the board.

Your problem is probably a timing issue. According to the datasheet the ON/OFF pulses must be greater than 90µS and less than 1S. So a pulse of a few millisecond should work fine.

If you are using just the module and have built your own circuit around the device, you will have to implement proper pullups/pulldowns. Reference the SIM18 Eval Boards User Guide for proper values and connections.

If you need additional help let me know.

BigDog

 

[Willykilly]

Hi,
I fixed the problem. As you said the timing had to be perfectly adjusted for the pulse to switch on the wake up mode. Also it was necessary to use a driver as the micro's pin could not drive the wake up pin. It looked strange but direct connection to wake up pin from micro did not work. Thanks very much for the help.
Thanks.

 

[danandan76]

Hi,
I fixed the problem. As you said the timing had to be perfectly adjusted for the pulse to switch on the wake up mode. Also it was necessary to use a driver as the micro's pin could not drive the wake up pin. It looked strange but direct connection to wake up pin from micro did not work. Thanks very much for the help.
Thanks.

Kindly help me to use sim18 GPS Module via SPI . If you have any details about how intialize, circuits kindly send me.