Basic comparison of some wireless options with Teensy: HC-05, XBee, and nrf24l01+ ?

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Electric Potato

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Hey guys,

I'm making a wireless MIDI controller involving two Teensy 3.1's, with one sending instructions to the other which then outputs midi via a standard cable to a computer, keyboard, etc. I've seen a couple different options at super different prices and was wondering if there are any considerations I should think about when looking at XBee, HC-05, and nrf24l01+ modules, the former being like 40-50 for two and the latter being a couple bucks for two. I need a range of a couple meters maximum, and speed isn't that important for the wireless part, (the receiving teensy will send midi stuff at 31250 based on whatever wireless commands roll in). I know they're different protocols, is there a reason to choose one over the other?
I've seen people using the nrf24l01+'s with success and will probably snag a pair, but I am curious as to whether I would have any reason to spring for some xbees in my pretty minor situation.

Thanks!
 
consider this free software and one the several radios it supports. I recommend the RFM69H for either 433MHz band or 902-928MHz band in No. America or 868MHz in the EU.
http://www.airspayce.com/mikem/arduino/RadioHead/

I don't like the nrf24l01 as it is 2.4ghz, competing with wifi, has the range disadvantage of 2.4ghz, and IMO it's too barebones.

but if you need just 2m range, things change. I'm thinking 200m.
 
I was just looking at the docs there - they seem complete and good - wish more libraries had that. That library is included in the Teensy install : "...\hardware\teensy\avr\libraries\RadioHead\examples\nrf24". Hoping for Teensy Tuned low impact performance.

I've got the nrf24l01's for my project as I'll be outdoors - now I just need to wire them up and make them go.
 
I have no trouble getting 10 m range in the house using the nRF24L01+ with just a pcb antenna with sheetrock walls in the way. I'm sure outdoors I could get many more tens of meters range. Great and easy to use libraries, low cost, and an appallingly small form factor, what's not to like about the nRF24L01+?
 
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Haven't seen if anyone shared SPI Radiohead on the nrf24L01 and the PJRC TFT?

Also wonder if the LC works - on one or both SPI ports with the Radiohead? I'll be using 3.1's - but seems like the LC's could be useful for debugging.

30M indoors sounds promising for outdoors - of course I can't get WiFi in my house much over 30 feet the way it is built, and as stevech noted the 2.4ghz band will get noisier.

I have one of those appallingly small onehorse units I'll be putting pins on.

**onehorse - check your http link.
 
RadioHead looks amazing. I especially like that it deals with acknowledging transmissions and that it works with Serial, RS485, as well as wireless communications. Error detection, retries, etc. all implemented. Impressive!

Unlike EasyTransfer, it won't work over I2C, but in return it offers variable-length/content messaging, which is a huge benefit in terms of maintainability.

Awesome. Want to send those guys multiple packs of beer if it works as well as it promises to.

The only missing item from the RS485 driver seems to be the TX_Enable feature that Paul developed, i.e. toggling the TX pin until the buffer is empty and then putting a half-duplex transceiver back in receive mode.
 
Mike at RadioHead hasn't adopted SPI Transactions.
IMO, one reasoning is that a real time wireless protocol usually cannot cope with high latency in the interrupt request for arriving message packets. High latency means a couple of mSec. This applies to reliable datagrams and to mesh relays.
So a real time thing like wireless networking with a practical protocol stack (versus a simple point to point link without relays or error detection/correction), and with low latency interrupts, should not share the SPI port unless the other SPI use blocks the radio's interrupt for a mSec or so at most. SD cards and other high volume transfers are not in that category.

Oh how we wish the T3 had 2+ SPI ports.
 
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