CAN-Controller board now talks

Showroom for MicroPython related hardware projects.
Target audience: Users wanting to show off their project!
Post Reply
tecdroid
Posts: 27
Joined: Thu Apr 08, 2021 6:22 am

CAN-Controller board now talks

Post by tecdroid » Sat Dec 04, 2021 7:27 am

Hi,

I built a can controller board upon stm32f405 to replace an old avr based pcb. I'ts basically the stm32 and a mcp2551 bus driver but anytime I try to send something, bus goes to state 3 or 4.. Since I use the most common controller for mp (as far as I know) I don't think it's a software issue.
It seems that my board sends something but the signal is very weak.. (just a few mV difference between H and L)
I tried to connect a can debugger and it also cannot receive anything..

So, could there be any hardware issue? I measured more than twice if there is any connection that must not be, so my pcb is same as this image. besides.. i removed the resistors behind the bus leds just to test if they were the reason for my problems.. - they obviously weren't

Image

Edit: I don't know why but this morning, it worked! (which always scares me) Only thing I did was measuring all connections.. Maybe there got some cosmic bits stuck? ... however..
Next, I'll try to re-solder the led resistors - even if I don't know how.. they are 0603 sized..

ph1lw21
Posts: 2
Joined: Sat May 08, 2021 8:54 pm

Re: CAN-Controller board now talks

Post by ph1lw21 » Mon Dec 06, 2021 1:19 pm

Your problem could be that the MCU is a 3.3V device while the MCP2551 is a 5V device. You will need voltage translator between the MCU and the transceiver or you need to choose a 3.3V transceiver.

Post Reply