How to use the MAX32's on-chip RTCC? (Real Time Clock)

Created Sun, 26 Jun 2011 18:06:33 +0000 by TECH GEEK

TECH GEEK

Sun, 26 Jun 2011 18:06:33 +0000

Earlier I saw that the Uno32 has a RTC on the Uno32's main chip, I also noticed that the Max32's main chip has one too. However the problem I face is that only the Uno32 has a spot for a crystal and on board caps, where as the Max32 only has connections to the on board RTC pins.

Basically I want remove the two diodes (D7G2) on pins 4 & 75 as well as the two 200ohm resistors (R5 & R6) between the RTC pins and pins 4 & 75 and replace them with a solder bridge. Then connect a 32.768k crystal to the pin 4 and 75 and a 30pF from pin 4 to GND as well as on pin 75.

Will this allow me to use the RTC?

Thanks

GeneApperson

Mon, 27 Jun 2011 15:44:10 +0000

In theory, that would work. You might have to tinker with capacitor values to get the oscillator to start up and run reliably. I've had problems getting 32Khz oscillators to run without playing with the capacitor and resistor values.

Another option would be to get a 32Khz oscillator with 3.3V CMOS output and connect to the SOSCI pin. This would probably work more reliably. You can get them in DIP packages, but there seem to be more options in surface mount. You could glue a surface mount oscillator upside down to the board and jumper wire for power, ground, and output. This would probably be easier than swapping 0402 capacitors and soldering in the crystal.

Gene Apperson Digilent

squiregeek

Sun, 08 Jan 2012 20:19:31 +0000

Gene,

By SOSCI, do you mean that pin directly or RC13 wired to R5? Would I need to yank (and bridge) the resistor to feed the oscillator? Thanks, Jim

majenko

Sun, 08 Jan 2012 21:03:28 +0000

A logic-output oscillator chip (or circuit) would work fine through the resistor. It's just another digital input signal.

jmp2612

Thu, 19 Jan 2012 16:46:57 +0000

what i did to make the rtcc work was i made a litle pcb card ( like the one i have attached ) with a conection to the 75th pin (SOSCI) of the MAX32's card and the 4th pin (SOSCO).

I used a 32.768kHz oscillator, and it worked with 18pF ceramic capacitors and also i tryed with 22pF capacitors and it also works well.

Hope this helps

onigas

Sun, 20 Jul 2014 08:33:08 +0000

From where can i download "rtcc.PNG"? Thank you for replay.