Serial LCD kit questions

Components & Accessories Displays
1

Hi

I have some questions regarding the Serial LCD kit:

I use a variety of serial (RS232) devices such as GPS, echosounder and scales which out puts a NMEA string at about 5Hz.

e.g.

$GPRMC,183729,A,3907.356,N,12102.482,W,000.0,360.0,080301,015.5,E*6F

$GPRMB,A,V*71

$GPGGA,183730,3907.356,N,12102.482,W,1,05,1.6,646.4,M,-24.1,M,*75

$GPGSA,A,3,02,07,09,24,26,1.6,1.6,1.0*3D

I would like to know if I connect these using a RS232 shifter (to convert the RS232 to serial TTL) will the NMEA sentence be scrolling on the LCD display.

This would make the Serial LCD a very handy device tester during fault finding.

My second question is what is the 5V power input tolerance? I see some of my devices output about 5.2V. Will the board be able to handle this or do I need to put some voltage regulator in my build?

2

Hi Wilhelm.

Technically that would work, but the data would probably be scrolling by so quickly that you wouldn’t be able to really see what’s going on. You’re also only going to be able to see 32 characters of data at a time which doesn’t give you much of a window into what’s going on. If you can pause the output from your device, you would be able to see the last 32 bytes of data that were sent though.

As for voltage, 5.2 volts would be the absolute maximum I’d feed that kit. Any higher than that and you risk burning something out.

3

thank you for the response.

Reading the actual values of the string is not important, if you can see $GPS… you know the data is coming in, the baud rate is correct etc.

The problem is if you see binary characters coming in or worse nothing at all.

Wilhelm

4

Hi have tested my outputs on RS232 DB9 connector and found that I do not have clean 5V power.

If I want to use an external power sources or battery pack how would I connect the RX/GND/5V?

The RX will come from the DB9 pin 3,

The 5V will come from the battery pack or 5V wall charger

But which common ground (GND) do I need to connect?

  • GND from the DB9 pin 5

  • GND from my power source?

    • regards

    Wilhelm

    5

    Hi Wilhelm.

    The signals coming from a DB9 serial port are RS232 serial level signals (+12v / -12v) and are not compatible with the Serial Enabled LCD Kit which is expecting TTL level serial. (+5v / 0v) You would need something to convert RS232 to TTL between the two devices.

    The ground from your RS232 side would connect to ground on the display side and the power supply ground connects to ground on both.

    I don’t know what specific pins are in use on your particular device, but it would look something like this:

    Untitled.jpg

    6

    Thanks

    I do have a RS232 to TTL converter (Sparkfun RS232 shifter)

    regards