nRF8001 , lowest data rate , TX current @ 0 dBm "P out" for the lowest data rate.

[Al Freeman]

Hi there ,

i am developing a biomedical recorder which needs to continuously transmit the recorded data , 

data rate is very low (9.6 Kbit/s  to  32Kbit/s) but i have a very limited power supply so low current consumption is crucial .

nRF8001 is suitable for my system in many cases and i wonder what's it's lowest data rate and also TX current @ 0 dBm "P out" for the lowest data rate (for continuous transmission)

Thank you, 

Al

[run_ar]

Hi,

I would actually recommend the nRF52810 if you are looking for a low power and cheap connectivity chip. We have an Online power profiler for the nRF52832 here: https://devzone.nordicsemi.com/power/. Unforuntatly it is not updated for nRF52810, but that is expected to be lower. Current consumption scenarios here: http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52810.ps/chapters/current_consumption/doc/frontpage.html?cp=2_2_0_4_1

For the nRF8001 you can take a look at the power consumption calculator in nRF go studio.

[Al Freeman]

Hi ,

The reason i chose nRF8001 was not having MCU , its not needed for my system and it can add more complication to it.

using "nRF go studio" is not very straight forward , is there quicker and more convenient way to find the current consumption for  lowest data rate and P out 0 dBm ?

Thanks

Al

[run_ar]

Maximum throughput with the nRF8001 is one 20 byte packet per 7.5 ms: ~21 Kbit/s. Please see the picture below for current consumption at this datarate.

Here is the result for doing the same with the nRF52832. Note that we have connectivity and uart implementations that you could use if you only want a connectivity chip.

Test setup

• Chip: nRF52832QFAAB0
• Softdevice: s132 2.0.0
• 32MHz crystal (HFXO)
• 32kHz crystal (LFXO)
• Sleep clock accuracy master and slave: 20 ppm
• DCDC enabled

Estimated values

BLE event total charge:	5.8 uC
BLE event total length:	2.4 ms
Average BLE event interval:	7.5 ms
Total average current:	781 uA

[Al Freeman]

thank you ! this information was very helpful. 

I appreciate that you shared the same information for nRF52832 as well  (781 uA  vs 4014 uA is significant in my application),

i have one more question , I read in many literature that BLE is not optimized for continuous data transmission but in our system data will be fed continuously from and ADC , do i need to buffer my data before sending it to uart port of nRF52832 ? 

thank you

Al

[run_ar]

Good question. It would probably make sense to have a buffer for that. On the nRF52832 you can buffer a maximum of 6 packet per connection interval interval in the SD. So you might also want to add a buffer between uart and ble so they do not depend on each other, as I do not think the ble_app_nus example is optimixed for speed.

Note that I might have mislead you a little in my comparison between nRF52832 and nRF8001 as you also need to include uart power consumption on the nRF52832 while spi is already included on the nRF8001 (at least I think so). however even with uart the avarage consumption would be way lower than the nRF8001.

Br, Runar