SD Write Problem

RE: SD Write Problem

Jørgen Holmefjord — Wed, 15 Nov 2017 13:45:18 GMT

Are you seeing any write errors reported in sdWrite function? I would recommend that you check all error codes related to writing to SD card and check with a debugger that the missing samples are actually sampled and tried written to the card. It would also be interesting if you could measure the current on the nRF chip only, to see if the excessive current is drawn by the chip or the card.

RE: SD Write Problem

bryanhsieh — Mon, 13 Nov 2017 21:13:39 GMT

Hi Jorgen sorry for the late response but I have added the relevant code. I mainly debug in RTT viewer, I haven't tried debugging in Keil for this project yet. To measure the current, I am using a DC power analyzer attached to the input of the DC boost converter, so the current is increased for the whole circuit.

RE: SD Write Problem

Jørgen Holmefjord — Mon, 06 Nov 2017 15:22:16 GMT

Could you post the code showing how you write to SD card? Is the increased current only for nRF chip, or for whole circuit? Have you tried to debug to see if the chip is stuck on some blocking function when the current is increased, preventing sleep and blocking processing of events?

RE: SD Write Problem

bryanhsieh — Mon, 16 Oct 2017 15:23:01 GMT

I think there are not being written to the SD card as if you look at the first graph, there is a gap(white line) at every 200 samples (10 seconds). And looking at the power consumption with a DC power analyzer(figure 2), I found that these gaps correspond to the sudden increase in write current of the SD card from normal spikes of around 20ms to a prolonged one of around 200ms.

RE: SD Write Problem

Jørgen Holmefjord — Mon, 16 Oct 2017 15:13:17 GMT

What do you mean when you say you lose samples? Are they not written to SD card, or not sampled? Are you seeing any errors when writing to the card?

RE: SD Write Problem

rct42 — Mon, 16 Oct 2017 02:41:48 GMT

Writing to SD cards is often more difficult than people expect. Although I haven't used fatfs for a while (I've moved to Keil's FlashFS), the general principle is "write" your samples into a large as possible ring buffer stored in RAM. I presume your ADC samples are done in an ISR? Meanwhile in your main loop, continuously check this ring buffer. If there is a complete block (usually 512 bytes) to write out, call f_write to write the data out to the SD card.