Standalone stm32 « LeafLabs Garden

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Standalone stm32

(10 posts) (4 voices)

Started 2 years ago by DofD
Latest reply from DofD

DofD
Member

Recently I started a guitar pedal project and I decided I was going to need more processing power than my standard arduino. I designed a pcb for an adapter board for a 64lqfp to break out the pins I needed.

With some fidgeting and adding some buttons to the BOOT pin I can now succesfully upload whatever I want to the microchip. Both the flash loader demonstrator and stm32loader.py tell me everything's okay.

Sadly, that's where it stops. Except for programming the board shows no sign of life. Got any idea what I should check? When using the maple bootloader the LED to pin 21 doesn't flash at all.

Posted 2 years ago #
DofD
Member

Let me elaborate.

The IC I use is an STM32f103RBT6 I picked up from farnell.
You can find my eagle schematic here: https://www.dropbox.com/l/4mNdHHpvTzB28iSUsEw1ff
I added wires to connect the vcc pins and I added some buttons with the appropriate pullup puldown connectors.

Posted 2 years ago #
DofD
Member

I feel like an idiot. I shorted one of the crystal leads to ground with an obvious solder blob.

When I start it up the LED blinks now! Small step for a man :)

The thing is, after the initial burst blinks the led won't stop its slow blinking. Just like when it's in perpetual bootloader mode. I tried actually entering perpetual bootloader mode and that changes nothing.

It also doesn't show up as a USB thing, ever.

Posted 2 years ago #
ala42
Member

You did flash the maple bootloader to 0x08000000 ?
Your board uses the same crystal frequency as the maple ?
Which voltage level do you have on the BOOT0, BOOT1, NRST lines ? They should not float.

Posted 2 years ago #
DofD
Member

I did flash it to 0x08000000. I think. The @ (h) option in flash loader demonstrator says 8000000.

It uses an 8.000 MHz crystal with two 18 pf capacitors

BOOT0: resistor to GND (measured 0v)
BOOT1: pulled to GND (measured 0v)
NRST: resistor to vcc (measured 3.3V)

Posted 2 years ago #
DofD
Member

I figured out something cool: I got the pinout for my stf202 the wrong way. I swapped usbdm and usbdp and made sure they reached the appropriate pins on the ic.

It now shows up as a USB device! =D In device manager it says 'Maple003' under LibUSB-Win32 Devices.

This confirms my earlier suspicion about it not being able to leave perpetual bootloader mode. Are there any cheatcodes I forgot to try?

Posted 2 years ago #
mlundinse
Member

You must flash a program, or load one to RAM, before the bootloader leaves perpetual bootloader mode.

Posted 2 years ago #
DofD
Member

That's actually a great tip. Thank you very much! It's fixed now :)

While we're on the subject, does anyone know the function of the USB_P on pin 52? My board seems to work with and without it connected.

Posted 2 years ago #
gbulmer
Moderator

DofD - USB_P is not used by the bootloader. On Maple, it is connected to a voltage divider which is across the 5V USB input voltage (need to divide 5V for input to the STM32F). So it could be used to detect that the board is connected to USB.

(Full disclosure: I am not a member of LeafLabs staff.)

Posted 2 years ago #
DofD
Member

So it's just a way for my sketch to know it's connected to the usb port? In that case I'm going to remove the frankenresistors making my board ugly.

You've all been a great help!
Thank you very much!

Posted 2 years ago #

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