Picaxe 28X1 connected to XBee Pro

[Andres Rodriguez]

I have a working datalogging circuit that will go (eventually) inside a radio controlled airplane. The data gathered is stored in an EEPROM and after landing it is transferred into a laptop.
I would like to transmit the data directly to the laptop. I could use AXE210 with a MAX3232 connected to the laptop.
However the on-board XBee must be connected to the 28X1 on the datalogging circuit.
The attached schematic shows a partial circuit of the datalogger and the connection to the XBee that, I think, may work. Besides powering the XBee with 3.3V, do I need to do anything else?
Does the AXE210 work with the XBee Pro?

 

[Technical]

Should work. The AXE210 will work with the pro but you may need to upgrade the 3.3V regulator to a device that supports a higher current value, as the Pro has quite a large current drain.

 

[hippy]

Your BAT85 in the Enhanced Download Interface should ideally be between Leg 6 and 0V, not directly across the PC RX and 0V.

 

[ciseco]

Hiya,

I suggest running your picacxe at 3.3v too if you can as the inputs on the 28X are ST and often (in my experience) cause data to behave strangely (as the voltage from the xbee is borderline too low for them) especially apparent at above 2400bps, alternatively some sort of 3 to 5v data buffer would work(the guys here might be able to suggest something). My advice would be to breadboard first to make sure your happy everything works, it took me 4 weeks to find this out and drove me to utter dispare when the same circuit worked on the 8 & 18 versions but played silly idiots with me on the 28 & 40.

Cheers

Miles
________
DeSoto Deluxe

 

[Andres Rodriguez]

Gentlemen,
Thank you for the input.
Hippy, good catch, I corrected the circuit.
Technical, I could use a LD1117V33 regulator, would that be enough?
Ciseco, I'll bradboard the circuit before I commit to a PCB.

 

[ciseco]

The LD1117V33 is what I use

Miles
________
BMW E32 specifications

 

[hippy]

Don't forget to remove the 10K/20K 5V-to-3V3 voltage divider for the TX to XBee when running at 3V3.

 

[Andres Rodriguez]

The on-board XBee that will be connected to the Picaxe 28X1 will be transmitting data and never receiving. So I assume it is safe to run the 28X1 at 5V with a voltage divider between the output pin and the XBee RXD. A 3V3 regulator will be used to power that XBee Pro.
On the ground will be another XBee Pro receiving data from the airplane and transferring it to a Laptop via a MAX 3232. I mentioned that I would use the LD1117V33 because on transmit mode the XBee Pro operating current is 295mA.
However, in receive mode it is only 45mA so I assume that the circuit on the AXE210 will provide an adequate supply.

Hippy, Ciseco, please correct me if my assumptions are wrong.

Thank you in advance for your help

 

[hippy]

You're right : Keep the 10K/20K when PICAXE @ 5V, XBee @ 3V3. That will work.

I thought you meant run both at 3V3 where the 10K/20K isn't needed. My mistake.