Choosing between nRF905 and nRF24L01?

[Mahesh Venkitachalam]

What are the main considerations for choosing between nRF905 and nRF24L01+ for an application? Is it just the transmission range (distance) and the frequency? Are there any other factors?

[Øyvind Karlsen]

Hi,

The main factors to consider are, computing power, energy efficiency, range and frequency. In addition to the two you suggested I will also add the nRF51 series(BLE - 2.4GHz).

Energy efficiency, as a general rule of thumb the newer chip is very likely to be the most energy efficient. For this I would go for the nRF51 series, which outshines both the nRF905 and the nRF24L01+.

Range; the range for a radio system is obtained from a formula called Friis transmission equation, this equation depends largely on the frequency(higher frequency means lower range) and the link budget(difference between transmitted power and radio sensitivity minus added noise). The different link budgets(best case scenario), without added, noise are nRF905 - 110dBm, nRF24L01+ - 94dBm and nRF51 - 100dBm. This suggests that if you need the extra range, you would go for the nRF905 chip. See this post for some range calculations for the nRF905.

Frequency, as things go up in frequency, they go down in size, e.g. if you want to make something small go for the higher frequency alternative. Usually things also increase in cost as they go down in size, but for our three alternatives the costs will be roughly the same.

Computing power will usually also be better for the latest chip.

In summary I would go for the nRF51 if I was not limited by some range requirement.

[Mahesh Venkitachalam]

Thank you!