Hello I’m not sure which of these to use. My project will be to transmit GPS data from one Pic24 uC to another Pic24 uC, along with a few instructions to turn a couple of GPIO pins on or off. Data rate isn’t crucial 38,400 baud or less.
Each of the units will be using EM-406 from SFE, UART1 via ISR will gather the GPS information. The range of the units will be a couple hundred feet line of sight max.
I’m just not sure which of these to use, the maxbee using strictly UART as described in the datasheet, or the nRF24L using the SPI port.
Other considering criteria, I’ll probably use one of the SPI ports to talk to an EEPROM, to store the GPS data for later use.
The PIC24 has 4 UART and 3 SPI so pin space isn’t an issue. The issue is which one will be easiest to program and be able to work with the ISR driven GPS reciever.
Xbee’s use a radio/chip that meets IEEE 802.15.4. There are many vendors for these chips and many for FCC type certified modules (or the FCC equivalents in other countries, esp. for 2.4GHz). The XBee series 1 and XBee Pro use a Freescale 802.15.4 chip. Series 2 use Ember’s chip, and series 2 is mostly for ZigBee whereas Series 1 is mostly for smaller/simpler networks. All these vendor’s modules are interoperable, the beauty of a standard, along with insurance from some vendor dropping the product or going chapter 13. WIth this too comes economies of scale. Other than SPI, it’s also easy to talk to an XBee using a UART without need for RS232.
The proprietary radios are popular but arguably legacy from a time before there were usable standards for low power low speed (250Kbps) bi-directional data radio/modems.
I am an apps engineer specializing in wireless technology, and I got a chance to see these modules just a few weeks ago. They are incredibly simple and you can have them working in your design same day, literally.
I have used Nordic, BlueSmirf, the no-name proprietary serial radios, and recently XBee. Basically all of the wireless options that SparkFun sells.
I have completely standardized on XBee (Series 1) and found it to be simple, cheap ($19 if u look around), very reliable, and able to handle very complicated tasks if needed (thru API mode).
As an embedded systems designer, I find that Xbee’s make it super easy to implement a straight serial over wireless bridge (ASCII UART), but they also give me the opportunity to expand my functionality later if needed (via API mode). As long as your power is at the right level, you only need to connect 4 wires - Vcc, Gnd, Tx and Rx. Cant get much more simple than that!
XBee’s API mode allows you do things like control routing between nodes, retransmit, and the ability to control a hugh mesh network of devices from one central point. But that’s just overkill for 99% of the people here.