Stalker Pin Usage

Does anybody know what pins are used by the different components on the Stalker (i.e. SD card, RTC, and xBee)? It looks like the SD card uses pin 13 to indicate when data is written to it. One of my sketches was using a LED connected to pin 13 but the sketch had problems when data was written to the card. The sketch worked right once I moved the LED to another pin. I looked through the documentation but could not find the info.

Thanks in advance

I was also trying to get some more info from the documentation and from this forum but without success.
I buyed one Stalker couple of weeks agoo but am stuck.
So far I’d like to know:

  • Serial connector pinout (the one under the Xbee shield), can you confirm it is dtr, gnd, rx, tx, 5V ? maybe it should be better documented in the pdf…)
  • Maximum SD card size and limitations (sd types/brands, max size allowed and how to format it)
  • What and how are the usual ATMEL pins used/routed to the periferals like RTC, SD card and Shield as CRS2010 was asking in the previous post).

Thanks in advance,

I have been using the Stalker for 1-2 months and it seems to work good once you get it figured out. We have not heard anything from Seedstudio regarding pin usage but I think I might have it mostly figured out. Looking at the info for the SD card shield, it looks like it uses digital pins 9-13. I looked at a data sheet for another mfgs data-logger shield and it uses digital pins 10-13 for the SD card so digital pin 9 might be free and is only being used as a locator. The SD card shield can be found at:

According to the documentation from the data-logger shield, it uses analog pins 4 and 5 which agrees with the picture of the DTC real time clock as shown on this page:

I am using the UartSB V2.2 for comunicating with the Stalker. The serial connector pinout can be found on the datasheet on the product page:

Looking at the product picture at the top of the page, the pins are VCC, TXD, RXD, GND, DTR from top to bottom.

I am using a 2GB Kingston SD card formatted as FAT. I do not think larger HD cards are supported.

I’ve posted some variations of the Demo sketch on the Arduino forum that you might want to check out:

There is also a discussion in the Arduino Syntax and Program section with some interesting info regarding methods of freeing up RAM and alternate code. The link is:

I bought the Stalker and UartSB from RobotShop and they have been very helpful and have responded to my questions quickly. They also have Stalker documentation or their web site.

Sorry guys! My apologize for inadequate tech support so far, we will enhance it from now.

@CRS2010: Would it be OK for us to add your thread to our product page? That will help other people with their usage on Stalker. Thank you for the works!

@CRS2010: great! thanks for your support: this IS really useful info!

So basically we could say that on the stalker, if you use RTC clock and SD card, you will have following pins occupied: 4, 5 and (9), 10, 11, 12, 13. If 9 is confirmed not used this means 6 pins total. Sounds good. Maybe ESP can just confirm.

Thanks again,

ESP, no problem with linking to the info. I have been going to post the sketches here but have not got around to it. Regarding logging data to the SD card, sometimes the card or data file becomes corrupted if the Stalker is turned off or reset during writing. There are several things that can be done to alleviate this. First, if you are opening/closing the serial monitor often, make sure you give it a good 5-10 seconds between opening/closing for the card to initialize. Also, pin 13 LED lights up everytime data is written so if possible, wait for a period of inactivity to open/close the serial monitor or shut off the Stalker.

Another way of reducing this problem is to connect a Logging/Standby switch to a pin and then modify the sketch so that data will only be written when the switch is in the Logging position. Then the user should be able to safely change the SD card without powering down the Stalker. Another thing that helps is disabling the reset function. This can be done by connecting a 120 ohm resistor between 5v and reset. Detailed instructions can be found at:

Thanks - CRS

RTC use the RTC pin and the SD card just use the 10, 11, 12, 13. and the Xbee socket use the pin 0, 1 .

Thanks for your feedback ,and there will be some improvement in the future version.

@FreeZinG: so which one is the RTC pin? the 4?

and btw thanks to all for the support!! Will let you know how my final project will look like…


Again on the serial connector: the serial connection does not work (I receive the infamous avrdude: stk500_recv(): programmer is not responding error) so I suspect to have made something wrong, but I’ve checked the wiring many times and am not able to spot the issue.

I have one real serial from my PC at one side (DB9 connector) and the stalker at the other… the cable I made is done this way:

DB9 --------------- Seeeduino Stalker (pin 1 is close to the power input)
1 DCD ------- n/c
2 RxD ------- pin 4 Transmitted Data
3 TxD ------- pin 3 Received Data
4 DTR ------- pin 1 Data Terminal Ready
5 GND ------- pin 2 Signal Ground
6 DSR ------- n/c
7 RTS ------- n/c
8 CTS ------- n/c
9 RI ------- n/c
pin 5 5 Volt n/c

Does it sound ok to you (I also tried to invert pins 3 and 4 for TX and RX)?


Hi all,
ok I’m able to answer myself now: it’s just a matter that the Stalker board, unlike for example the Arduino Diecimila, is NOT including the serial level conversion circuitry on board!

So basically I was assuming that the Stalker was including the same conversions that I was having in the Diecimila, but this is NOT the case, the section like the following one is missing on the Stalker: … ransistor/

That is also why people using the USB adapter from seeedstudio do not have issues since this section is in place in the adapter (implemented with the classic MAX232 chip plus USB conversion instead of using two transistors of course).

Ok now that this is clear I knwo that the RX and TX signals from pins 2 and 3 need to go trough a MAX232 first! :wink:

Anyway I tought it to be worth to mention here, since it may not be so obvious when accustomed to other boards you may think completely compatible…


Hi again,
ok all fixed now with a small circuit using MAX232 here (had to put a 10k resistor in the stalker serial pin 3 and use rx and tx inverted to the MAX) and it works fine now! Great… if someone needs I can post details-schematic…

@FreeZinG says: RTC use the RTC pin and the SD card just use the 10, 11, 12, 13. and the Xbee socket use the pin 0, 1 .

So one still open question for me now is the pin(s) used by the RTC: looking at the libray I understood that RTC uses three stalker pins: 2, 3 and 4: is this correct, so it is three pins used by RTC… can someone confirm this is correct?


Now we use the DS1307 RTC , and it’s IIC interface , so the stalker use the A4 A5pin to control the RTC.