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Metro M4 Express SCL/SDA pull up vs Grand Central
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Metro M4 Express SCL/SDA pull up vs Grand Central

by basrijn on Fri Mar 27, 2020 2:11 am

Hi,

I have two ChronoDot RTC's. I have been using one with my Grand Central for a while without issues.

Just started using the second one with my M4 Express. Put two 10k resistors on it, plugged it in and the M4 express refuses the boot. The #13 LED barely comes on, windows host never makes the new USB device sound. I can unplug the power or SDA/SCL and the board boots up, I can plug the wires back in and the device continues to run OK.

Checked my other ChronoDot and I had used a 4.7k resistor, desoldered the 10k and put two 4.7k's in. Same issue. Swapped my known good from the Grand Central and it shows the same issue.

Thoughts?

/Edit: Just as I post this, on a hunch I moved the power for the ChronoDot to the 3.3V pin on the board. Now it works fine. I also have a Lora radio on the same board. I guess the two together pull to much current at boot time? Surprised this is the case, the M4 Express seemed like a fairly beefy board compare to the feathers.

Does this make sense?

Bas

basrijn
 
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Re: Metro M4 Express SCL/SDA pull up vs Grand Central

by adafruit_support_mike on Sun Mar 29, 2020 5:26 am

Post a photo showing your hardware and connections.. the DS3231 shouldn't use enough current to make a Metro fail.

800x600 images usually work best.

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Re: Metro M4 Express SCL/SDA pull up vs Grand Central

by basrijn on Sun Mar 29, 2020 8:30 pm

Hi,

I've attached a diagram of my setup, as as well as a photo.

I measured the voltage on the 5V pin feeding the ChronoDot, and the voltage is the same with the pin unconnected, or connected to the CD. With the pin connected, the board does not properly start until I unplug the power pin to the CD. If I run a wire straight from the 3.3V on the board all is well

Bas
Attachments
Start module_bb.png
Start module_bb.png (259.54 KiB) Viewed 82 times
Start module_img.png
Start module_img.png (819.3 KiB) Viewed 82 times

basrijn
 
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Re: Metro M4 Express SCL/SDA pull up vs Grand Central

by Statorworks on Wed Apr 01, 2020 8:14 pm

I've been trying to figure the I2C on the Metro M4 for a while. I've come to the conclusion the smaller devices don't have any I2C available.

See page 36 of the SAMD51 datasheet, section 6.2.6 Sercom I2C configurations.
I2C ported out only on the 100-pin and 128-pin parts. I wish I was wrong on this :(

Edit:
Never mind, I just downloaded the latest datasheet, it includes the information for the smaller form factors.
Although none of those match the PB02 or PB03 corresponding to the Metro's schematic [????]

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Re: Metro M4 Express SCL/SDA pull up vs Grand Central

by basrijn on Sun Apr 05, 2020 2:59 pm

I narrow this down a but further, the issue actually seems to be with the RTC.adjust function. Opening a new topic to ensure the title reflects the issue

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Please be positive and constructive with your questions and comments.