ESP8266 Community Forum

Posted: **Sat Jan 09, 2016 5:08 pm**

Hi,
I have following code :

#include "ESP8266WiFi.h"

extern "C" {
#include <user_interface.h>
}

byte rtcStore[1];
char trial[] = "[{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"},{\"T\":\"20\",\"H\":\"40\"}]";

void setup() {
  // Start Serial
  Serial.begin(115200);
  delay(10);

  Serial.println("Hello");
  // put your setup code here, to run once:
}

void loop() {
  delay(1000);
  rtcStore[0] = 10;
  Serial.println("Mem write rtcStore:");
  Serial.println(system_rtc_mem_write(65, rtcStore, sizeof(rtcStore)));
  Serial.println("Mem write trial:");
  Serial.println(system_rtc_mem_write(68, trial, sizeof(trial)));

  char t[sizeof(trial)];
  byte r[1];
  Serial.println("Mem read rtcStore:");
  Serial.println(system_rtc_mem_read(65, &r, sizeof(r)));
  Serial.println("Mem read trial:");
  Serial.println(system_rtc_mem_read(68, &t, sizeof(trial)));

  Serial.print('<');
  Serial.print(t);
  Serial.println('>');
  Serial.print('<');
  Serial.print(r[0]);
  Serial.println('>');

}

I have this output:

Code: Select all

r...lrß.#.ânÀ.à....ì.p|ß.ìx.Çäl.p...ònnä.;ònÄä...bcl`.$`.üpònàÃÜ..àÇÀl....bÀ.nâãnÀ$Ø.bÀÄ>~ònî.ÄÁ.l`.ü.Ü#nÀ..r....nrß;.ÄÀ.?.r...rßÛnÀ..àÇÄl`.üünÄbàHello
Mem write rtcStore:
1
Mem write trial:
1
Mem read rtcStore:
0
Mem read trial:
1
<[{"T":"20","H":"40"},{"T":"20","H":"40"},{"T":"20","H":"40"},{"T":"20","H":"40"},{"T":"20","H":"40"},{"T":"20","H":"40"},{"T":"20","H":"40"},{"T":"20","H":"40"},{"T":"20","H":"40"},{"T":"20","H":"40"}]>
<0>

As you can see readin rtcStore is returning 0 and that i don't understand. If i remove all the write/read code for trial variable then i can read rtcStore, it's like i am doing something wrong when i write trial but it works.

Any ideas ?

/donnib

Posted: **Sat Jan 09, 2016 8:18 pm**

I've some tries with system_rtc_mem_write() and system_rtc_mem_read(), which I've never did before, in my own Sketch_Buffet. I works without any problems.
So, I've copy/paste your own sketch, and I'm seeing the problem.
I didn't figure out yet where is the issue.
I will dig more ... :roll:

Posted: **Sun Jan 10, 2016 3:42 am**

If you read the SDK Guide about the RTC read/write functions it mentions being 4 byte blocks -

"Note: RTC memory is 4 bytes aligned for read and write operations. Parameter src_addr means block number(4 bytes per block)."

I don't completely understand the implications of that, but if you change your

Code: Select allbyte r[1];

variable definition in your sketch to be

Code: Select allbyte r[1] __attribute__((aligned(4)));

it seems to fix it.

Posted: **Sun Jan 10, 2016 10:07 am**

Yes, that is it ! I've tested it, and @torntrousers is right.

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