Greetings, I came along the pic where the arduino can read and write to a SD card in a socket simply wired and coded correctly. In my current project I use an Adafruit SD Breakout Board. I use the breakout board to log information and to play WAV. files. I don't have a socket at the moment to test this theory.
The Adafruit SD Breakout Board cost $7.50. A socket around 50 cents a few resistors maybe a quarter. I am trying to have a smaller foot print on my PCB and to save money. I need a hundred
of either if I can accomplish the same thing noted above. $75.00 is way better than $750.00.
One schematic came from here, the other from Adafruit. My question to you is, What am I getting for the $7.50 from the Adafruit Breakout Board that I wouldn't or won't get by simply going the with a socket and a few resistors?
You can run your ATmega328p on 3.3V but it is not rated for 16 MHz at that voltage. The easiest fix is to run your ATmega328p at 8 MHz using the internal 8 MHz RC clock. By running on 3.3V you can wire the SD socket directly and save money. You can also eliminate the 16 MHz crystal or resonator, thus saving even more.
"the breakout board has level conversion. SD cards work at 3.3 V, 328p usual voltage is 5 V"
The 328 runs on 5v regulated. It powers the Adafruit SD reader writer at whatever V the 328 puts out. It works fine. The SD is rated for 3.3 to 5 volts.
"You can run your ATmega328p on 3.3V but it is not rated for 16 MHz at that voltage. The easiest fix is to run your ATmega328p at 8 MHz using the internal 8 MHz RC clock. By running on 3.3V you can wire the SD socket directly and save money. You can also eliminate the 16 MHz crystal or resonator, thus saving even more."
I run at 16 MHz because there is a RTC involved. The internal clock is not an option. I use interrupts and the POWER_DOWN and SLEEP_MODES through out the project based on the time stamp of the RTC.
So... if I regulate the power to the SD read/write, will it perform the same tasks? Log DATA and PLAY WAV. files? I can't seem to find a SD Socket that is breadboard friendly to test the theory.
Fredric58:
The 328 runs on 5v regulated. It powers the Adafruit SD reader writer at whatever V the 328 puts out. It works fine. The SD is rated for 3.3 to 5 volts.
The SD card requires 3.3V. The Adafruit SD Breakout Board has a 3.3V regulator and a level shifter so it can be used on a 5V Arduino. The schematic you provided shows that the SD card is powered from the 3.3V regulator on the Arduino and has voltage dividers to make the Arduino's 5V outputs compatible with the SD card's 3.3V inputs. If you run the "Arduino" on 3.3V you can eliminate the level shifters, voltage dividers, and external the external 3.3V regulator.
Fredric58:
I run at 16 MHz because there is a RTC involved.
That is what we in the business call a "non-sequitur". The external RTC has its own clock and doesn't care what system clock you use.
What RTC chip are you using? Does it require 5V?
Fredric58:
The internal clock is not an option. I use interrupts and the POWER_DOWN and SLEEP_MODES through out the project based on the time stamp of the RTC.
Again, there seems to be a logical disconnect. How is the source of the system clock related to your usage of sleep modes and an RTC?
Fredric58:
So... if I regulate the power to the SD read/write, will it perform the same tasks? Log DATA and PLAY WAV. files? I can't seem to find a SD Socket that is breadboard friendly to test the theory.
The SD card should be happy and perform well as long as you provide it with enough 3.3V power and don't put more than 3.3V on any of the input pins.
"The SD card requires 3.3V. The Adafruit SD Breakout Board has a 3.3V regulator and a level shifter so it can be used on a 5V Arduino. The schematic you provided shows that the SD card is powered from the 3.3V regulator on the Arduino and has voltage dividers to make the Arduino's 5V outputs compatible with the SD card's 3.3V inputs. If you run the "Arduino" on 3.3V you can eliminate the level shifters, voltage dividers, and external the external 3.3V regulator."
So simply step down my 3.7v 18650 batteries to 3.3v and I can power my ATMegea 328 IC and run with a SD Socket. Log data and play WAV. files?
That sounds reasonable!
"What RTC chip are you using? Does it require 5V?"
DS3231 2.3v to 5.5v, no regulator or level shifter appears to be required.
"How is the source of the system clock related to your usage of sleep modes and an RTC?
I need an external clock for interrupts to get to deep sleep POWER_DOWN MODE. Sleep modes use internal clock.
The Amplifier I use is rated for 2.0v to 5.5v. Currently runs at 5v regulated. Not sure how a 3.3v input would affect the output (VOLUME)
