Mulitple i2c devices and sd_card

Projects General Guidance
1

I am building an irrigation controller using a UNO, it currently has a RTC , 4 keys managed by PCF8574, 4 relays controlled by the same PCF8574, a sd_card, and a 2x16 LCD and a moisture sensor.

The idea is that when powered on the irrigation schedule is read from a file on the sd_card and then the program is run which will turn on and off the relays.

Individually all the bits work, i can read and write to the sd_card, can see buttons pressed can turn on and off relays, can get the time from the rtc.

BUT, I find that the lcd and/or the RTC interfere with the sd_card. As the sd_card is not an i2c device I am at a loss to understand why,

Is anyone aware of why this would be the case and maybe point me to a discussion on the matter.

See

53  void setup() { 
56     //get_rtc_time();
236   //get_rtc_time();

i2c_play.ino (8.1 KB)

2

Please post code the way told in this guiding topic: How to get the best out of this forum - Using Arduino / Project Guidance - Arduino Forum

Helpers in general don't like downloads filling up their computers.

3

You need to reveal what you mean by the 'RTC interfere with the sd_card'.

Perhaps explain what actually happens ?

4

Posting a schematic as you have wired it would help us. Frizzy pictures do not do much. Also post links to technical information on each of the hardware devices.

5

Thanks.

Would not like to fill up your pc with a file that you could delete.

And, I had a frizzy pic, but you don't want that, eagle is $500 a year (hmmmm ) bit much for what i am doing.

Will battle on, thanks anyway.

6

O no :scream: please don't do that.

srnet asked a really important question : what is happening ? interfering can be so many things. Does the I2C bus halt ? Does the RTC not have the time anymore ?

This forum can put a sketch between code text, so we prefer that instead of links or attachments. That's how it is.

For those of us who are used to look at schematics, a Fritzing or Tinkercad picture can be really hard to understand. We have to convert it in our head to a normal schematic. That is not impossible, but we just like to emphasize that we don't like Fritzing picture.
Someone should make a T-shirt for nerds with the text: "Don't show me a Fritzing picture" :rofl:

You can draw a schematic on a piece of paper and make a photo of it.

KiCad is free and it can import Eagle *.sch files.
Some use a online schematic service, but I'm struggling too often with those.

You see, if you know the background, then the others were reasonable and to the point :heart:

7

Free for non-commercial use and up to 80cmsq double sided boards last time I checked.

8

KiCad is free although a donation is asked for but not required. It will work on most operating systems. I use Linux and my buddy uses Windows. That should fit your budget. I have been using it for several years and I like it. All of the PCBs I did with it came back correct.

9

How much memory usage does the compiler show? The SD library will need 512 bytes of ram for a buffer. My guess, without being able to compile the code, is that you are low on ram (dynamic memory).

Your sketch is using RTC_millis, which is a software RTC based off the millis counter, so no wiring problems from that.

Use the F() macro for any printed text literals, that will save some ram.