greets
The only way I know how receive data form multiple 2.4GHz transceivers simultaneously is to have the sending devices be "muted" unless a SlaveSelect (SS) signal instructs them to write to the wireless SPI bus, i.e. transmit.
What would happen if my neighbors would be using the same frequency, would simultaneous wireless data signals corrupt the data on the my wireless SPI bus?
Can you explain which transceivers you are talking about, and why they would
be simultaneously active. You shouldn't need more than one transceiver at each
node in a network, unless they were for different bands.
hi
it's the modules that are readily available on ebay. They are absed on nRF24L01+ .
By simultaneously I meant that someone in a neighboring apartment might be using transceivers running on the same frequency as mine and transmitting data at the same time my transceiver is transmitting.
I guess I'll have to make sure my transceivers don't operate on the same frequency.
Here is some info from the data sheet:
The nRF24L01+ is designed for operation in the world wide ISM frequency band at 2.400 - 2.4835GHz.
6.3 RF channel frequency The RF channel frequency determines the center of the channel used by the nRF24L01+. The channel occupies a bandwidth of less than 1MHz at 250kbps and 1Mbps and a bandwidth of less than 2MHz at 2Mbps. nRF24L01+ can operate on frequencies from 2.400GHz to 2.525GHz. The programming resolution of the RF channel frequency setting is 1MHz. At 2Mbps the channel occupies a bandwidth wider than the resolution of the RF channel frequency setting.
To ensure non-overlapping channels in 2Mbps mode, the channel spacing must be 2MHz or more. At 1Mbps and 250kbps the channel bandwidth is the same or lower than the resolution of the RF frequency. The RF channel frequency is set by the RF_CH register according to the following formula: F0= 2400 + RF_CH [MHz]
You must program a transmitter and a receiver with the same RF channel frequency to communicate with each other.
ok, so at 1MHz bandwidth that's 125 channels to choose from .
MultiCeiver™ is a feature used in RX mode that contains a set of six parallel data pipes with unique addresses. A data pipe is a logical channel in the physical RF channel. Each data pipe has its own physical address (data pipe address) decoding in the nRF24L01+.
nRF24L01+ configured as PRX (primary receiver) can receive data addressed to six different data pipes in one frequency channel as shown in Figure 12. Each data pipe has its own unique address and can be configured for individual behavior.
Up to six nRF24L01+s configured as PTX can communicate with one nRF24L01+ configured as a PRX. All data pipe addresses are searched for simultaneously. Only one data pipe can receive a packet at a time. All data pipes can perform Enhanced ShockBurst™ functionality.
ha, looks like this answers my question.
naut:
hiit's the modules that are readily available on ebay. They are absed on nRF24L01+ .
Yes, used them, they have a channel spacing of 1MHz and support 250kb/s, 1Mb/s and
2Mb/s
By simultaneously I meant that someone in a neighboring apartment might be using transceivers running on the same frequency as mine and transmitting data at the same time my transceiver is transmitting.
You may lose packets then. Nothing you can do but detect and retransmit - there
is support on the transceiver for automating this IIRC
I guess I'll have to make sure my transceivers don't operate on the same frequency.
Other issues are that every WiFi router and microwave oven is also operating in
that band - you may have to hunt around for the best channels. You'll get better
range on the 250kb/s setting, but the range is poor anyway because its 2.4GHz,
shorter wavelengths mean smaller aerials, smaller aerials mean less range,
all else being equal.
Other issues are that every WiFi router and microwave oven is also operating in
that band - you may have to hunt around for the best channels. You'll get better
range on the 250kb/s setting, but the range is poor anyway because its 2.4GHz,
shorter wavelengths mean smaller aerials, smaller aerials mean less range,
all else being equal.
oh, I'm actually thinking of using these transceivers for MIDI data, 250kb/s is way more than I need. Perhaps these transceivers are overkill for MIDI.
If you want reliable, or even lossless communications, you will need to use error correcting transmission and reception methods with acknowledgement packets. If you go that route, that you can't achieve actual information transfer anywhere near 250 Kbps.
Based on my experience with the 2.4 GHz Wixel modules from Pololu, using a bit rate of 250 Kbps or even 350 Kbps, you might expect something like 10Kbps of actual lossless communications. This rate is about the same as 9600 baud serial communication.
Interference will always be a problem, no matter what techniques you use!