Re: BlueSaab 6.1 - No "BlueSaab" Bluetooth device available after power up

Posted by Seth on Sep 23, 2019; 5:49pm
URL: http://bluesaab-forum.90.s1.nabble.com/BlueSaab-6-1-No-BlueSaab-Bluetooth-device-available-after-power-up-tp1492p1528.html

So you’re applying 3.3v to the EXT VCC pin, and you get that ripple? I was going to suggest looking at the vreg to make sure it’s putting out 3.3v...

It could be the oscillator or a bad connection to it; much easier to try that than the stm32...

Also, it’s hard to read the oscillator with a scope without “breaking” the oscillation due to extra impedance that the oscope leads introduce...but that’s just what I’ve been told, I’m not a EE. But at least you did see it sometimes.

Thanks for not bashing us and working with us to get it sorted out. 

Seth

On Mon, Sep 23, 2019 at 13:38 czabel [via BlueSaab Forum] <[hidden email]> wrote:

OK, I just beeped out every pin pair on the STM32, nothing shows a bridge.
I get slight hiccups on the Vcc/Gnd pairs, but that should just be decoupling caps charging up. Expected behavior.

I got a scope on the Osc, and found some interesting behavior. Screenshots incoming:

Zoomed out view: You can see there is a periodic hiccup, happening with a frequency of 1kHz.


Zooming in: there's a lot going on in this hiccup, including square waves.



Most of the time, it's a good 8MHz waveform:


Having said all that... This only shows up when I connect power to the "EXT VCC" pins. I get NO WAVEFORM on the Osc when I connect my FTDI cable to the FTDI header, it's tied high at 2V.

VDD/VSS are reading what I would expect: power and ground.

On the RN52 side of things, I'm reading the following:
Pins 3, 5, 11, 21 (STATUS, RESET, CMD, PWREN) are all low.
Pin 16 (UART_TX) is high, at 3V.
Pin 17 (UART_RX) is low.

So, given that I only see the oscillator working when the STM32 has 5V, and not even consistently... I'm just going to buy a few more of both the oscillator and the chip, and try again. Not the most fun thing... Getting the STM32 off the board might be a bit of a pain, but unless you have any insights here Karlis, I'm stumped.

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