1

I need to store about 1 adc sample per second on a wireless project for about 10 hours. The problem is the energy. What is more efficient a constant transmission on BLE or writting each second on a SD Card. Also I was thinking in two boards that can do the job because it has all in in them (The SD module and the BLE module)

RedBearLAB for BLE Alternative

or Adafruit Feather M0 or Adafruit Feather 32u4 for writing on SD

Pulse9
  • 489
  • 7
  • 20
  • 2
    Neither. Writing (or transmitting) every half hour or so, when your several-kilobyte buffer in CMOS SRAM fills up. –  Apr 11 '16 at 21:15
  • An adc sample of 8 to 16 bits is too small for the minimum SD sector size of 512 bytes. So you would have a lot of overhead, reading, appending, rewriting. You want to cache these ADC samples to a larger size before writing. See http://electronics.stackexchange.com/questions/227686/sd-card-sector-size – Passerby Apr 11 '16 at 21:30
  • Im using an arduino with an SD Module, Im creating a .txt file with CSV of all the samples, but now I need to make it wireless, transmitting by BLE or Store in SD with a battery, I think I can do the same with the SD Module, creating a file so I can fill the sector size. – Pulse9 Apr 11 '16 at 21:47

1 Answers1

2

it depends :)

did you think about the ble profile which you like to use?

Do you have the possibility to buffer some samples in your MCUs RAM -- and then forward a block of samples to your SD or via radio. The most power will be saved if your MCU disables all peripherals most of the time AND your ADC runs timer triggert (CPU etc off) ... and if possible, you stay for several sec. and then handle the collected samples.

by the way, how much energy you have for the 10 hours?

twooBeers
  • 46
  • 2
  • Oh, that could be great, I can probably store a 15 minutes sample block (1Sample/Sec *60s * 15m= 900 samples in RAM) and then write a 15 minutes sample block right? probably is better way than transmitit by bluetooth all time – Pulse9 Apr 11 '16 at 21:33
  • yes ... if you have no other constraints -.. collect as much as possible. – twooBeers Apr 11 '16 at 21:38
  • may your ADC contains a sample buffer or you can configure a DMA to forward data to RAM without CPU interactions. – twooBeers Apr 11 '16 at 21:41