frequency and sd card operations

[ehobart]

Hi,

I need to log data to the sd card for a year in a battery powered instrument and though the Micropython would be a good choice.
I found that although the USB and sd card appear to be working at 48 MHz I consistently get an OSError: 5 when I open a file.

After experimenting I found the minimum speed where all works is 64 MHz. Is there any more information on running the board
slower and retain sd operations?

Thank you,

Edward Hobart
Research Engineer
Woods Hole Oceanographic Inst.

[blmorris]

Hello Edward-
I haven't done any research along the lines you are describing, but I'm wondering if you have tried experimenting with different clock speeds with USB disabled. Presumably a battery-powered instrument won't need to have a USB connection, and without it you may be able to bring the clock speed down quite a bit.
You can disable USB by putting pyb.usb_mode(None) in boot.py, and use pyb.repl_uart() to select a UART to use the REPL (you will need a USB-serial converter for this step.)

See http://forum.micropython.org/viewtopic. ... =620#p3535 which is where Damien made the same suggestions to me for assisting with C development on the pyboard.

-Bryan

[ehobart]

Hi Bryan,

Good suggestion!

At this point I'm doing a blunt force look at power reduction. If the system gets deployed I'll have go through

everything I can do to reduce power. Part of creating long deployment oceanographic instruments.

Ed Hobart