Question about XBee

[ck88]

Hi,

Thanks for the reply.

I've attempted connecting the circuit according to the SKXBEE manual (without the switch button), however so, when I output a HIGH from the PIC pin, the collector's voltage is only around 0.45 V. Hmm, strange? In the code, I inserted a delay of roughly 1ms between HIGH to LOW transition. Well, if a transistor is used, the flow will be reversed as in a HIGH is needed to reset XBee and not the usual LOW to reset XBee, right?

Thank you.

[ABSF]

No, you need a LOW on the reset pin to reset the XBee. Just see how the button is connected to get the clue. Thats why the transistor C/E is connected directly across the push button acting as a PB switch. And that's also why you need a Hi on transistor Base to rest the XBee.

The transistor is pulled high internally in the SKXBee and that's what shiyan was mentioning about the "Open Collector" of the transistor. As shiyan didnt know the Reset pin is pulled high using 3.3V or 5V, so using an open-collector transistor to reset the XBee is the safest.

Allen

[ABSF]

Checking the User's Manual of SKXBee it show that the connection to RESET pin is optional. It seem to be me if you don want to reset it from PIC, you can waive the transistor and the extra push button function is the same as the reset button on the SKXBee. NPN transistor, a good way to sink current at pull the collector to GND. Yup, I think Cytron designed the SKXBee to be have a pull high resistor on board at XBee's reset pin, so by default the XBee is not reset (Reset require low). So no external pull high is needed to make it work. If you want to reset it, pull this pin low by either push button (mechanically and electrically) or use a NPN transistor to do that which can be control by a microcontroller output pin. A good method

You see..... you have missed out the important points mentioned by shiyan. I dont know where you get the ideas that you need a HIGH to reset the XBee.

Allen

[shiyan]

Checking the User's Manual of SKXBee it show that the connection to RESET pin is optional. It seem to be me if you don want to reset it from PIC, you can waive the transistor and the extra push button function is the same as the reset button on the SKXBee. NPN transistor, a good way to sink current at pull the collector to GND. Yup, I think Cytron designed the SKXBee to be have a pull high resistor on board at XBee's reset pin, so by default the XBee is not reset (Reset require low). So no external pull high is needed to make it work. If you want to reset it, pull this pin low by either push button (mechanically and electrically) or use a NPN transistor to do that which can be control by a microcontroller output pin. A good method

You see..... you have missed out the important points mentioned by shiyan. I dont know where you get the ideas that you need a HIGH to reset the XBee.

Allen

Just notice my reply have a lot of typo.... sorry about that Busy working

Anyway Allen is right, you will need to give high to the transistor base in order to enable the NPN transistor to "connect" the collector to emitter by sinking current from collector. So if the RESET pin on SKXBee is pull high to 3.3V or 5.0V which I am not sure, it will still be low, further provide a reset to XBee on it. As you tested, when you provide high from PIC to transistor, the collector is 0.45V, that is very low voltage and mostly will be "see" as logic low to Reset pin of XBee module.

I am curious to know, when you measure 0.45V at RESET pin, why don you test your setup? As Allen pointed out, if you connect external button to the SKXBee Reset pin, and press the button what is the voltage at RESET pin? 0V, right? is almost the same level as 0.45V..... the rest you should know