Posted by
czabel on
Sep 23, 2019; 5:38pm
URL: http://bluesaab-forum.90.s1.nabble.com/BlueSaab-6-1-No-BlueSaab-Bluetooth-device-available-after-power-up-tp1492p1527.html
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.
2000 9-5 Aero 5-Speed