Holux GPSlim 236 on Seeeduino Mega (Arduino Mega)

On Saturday I received my Seeeduino Mega which is a Arduino compatible ATmega 1280 based board, which provides 70 (!) IO Ports. Thanks to Klaus Sander for the quick overnight delivery!

I followed Mikes example and connected the Serial TX of my GPSlim 236 to a (Soft) Serial RX Port of my Arduino.
The GPSlim 236 has a Mini-USB breakout which in fact is no USB but a serial port (thats the reason why you would need a converter cable (USB-to-Serial) if you want to connect the device via cable to your pc).
You will find GND on the black wire, TX on green, RX on white. You can supply +5V on the red wire to power the device and load the battery (when there is one in). If you want to use a USB adapter on breadboard or something similiar you can find the USB pinout here.
For the very basic beginning I connected only GND and TX, powered the GPS device via battery and looked if there is some data coming.

Because I am using a Mega board I had to modify some things (ie using the current beta 11 of NewSoftSerial).

Testing Suite for Holux GPSlim 236 GPS on Seeduino Mega
by KaiK ()
Code last modified 29.07.2011

GPS serial pinout and inspiring code at http://mikenz.geek.nz/blog/gpslim236_arduino/

NewSoftSerial (Version 11) library compatible with "Megas" from http://arduiniana.org/2011/01/newsoftserial-11-beta/
Note: Not all pins on the Mega and Mega 2560 support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 50, 51, 52, 53, 62, 63, 64, 65, 66, 67, 68, 69

TinyGPS (Version 10) NMEA parsing library from http://arduiniana.org/libraries/tinygps/


SoftwareSerial gpsNSS(50, -1); //Currently only Receiving data, no ACK or sending needed
TinyGPS gps;

void setup()
/* Serial output */
Serial.println("Waiting for GPS");

/* Start GPS */

void loop()
while (gpsNSS.available()) {
if (gps.encode(gpsNSS.read())) {
float lat, lon, alt;
unsigned long age;
gps.f_get_position(&lat, &lon, &age);
alt = gps.f_altitude();

/* Display new GPS data when we get it */
Serial.print("Lat: ");
Serial.println(lat, 5);
Serial.print("Lon: ");
Serial.println(lon, 5);
Serial.print("Alt: ");
Serial.print(alt, 1);

Serial.print("Fix age: ");


It worked very fine.

After that I measured the current draw of the Holux GPSlim 236 to determine which power supply to use. In fact you cannot use the Arduino on board power for this. I soldered a little board/shield where I provide power and some pinouts. The whole device gets powered by some external source.

Maybe later I will use the RX port of the device to query a specific dataset or change configuration (ie refreshing rate) in live mode (see NMEA Data, ie $PSRF103 codes).
Note: For TX from Arduino you dont need a port with interrupt, so you can use every (!) port.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s