I have been looking in the Marlin firmware for about an hour or two now to find what pins I should use for UART for my tmc2208 drivers and I have come up with nothing.

Does anyone know what they are or how to assign them? BTW, I am using the regular version of the RUMBA board not the RUMBA+ version.

For somereason i didn't put that i want to control my stepper motor drivers through uart they are tmc2208

  • $\begingroup$ Why do you need the UART? What are you trying to achieve? Do you want to reflash the firmware? $\endgroup$ – Greenonline Jun 5 '19 at 22:41
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    $\begingroup$ Is it a genuine RUMBA or a Chinese clone. I have both RUMBA boards and found that the Chinese clones cut corners and as such some things don't work. E.g. the exposed USB pin header on the RUMBA+ is totally unusable when you properly connect it, the board stops working... $\endgroup$ – 0scar Jun 6 '19 at 7:57
  • $\begingroup$ sorry i didn't put that i wanted to use uart for my tmc2208 drivers my bad. $\endgroup$ – lolatron Jun 7 '19 at 2:56

The RUMBA schematic is available on the RUMBA wiki.

RUMBA schematic

From the schematic, I see that UART3 (with +5V logic levels, not RS232) is presented on the EXP3 connector. I don't know if Marlin firmware can be controlled through a UART other than UART0, which is converted to USB through an FDDI chip. The Arduino bootloader is not expecting another UART, so you may still need to program it through the USB port (and UART0).

  • $\begingroup$ Did you mean FTDI (i.e. FT232RL) and not FDDI? Also, the RUMBA appears to use a 16U2 to implement USB, not an FTDI. $\endgroup$ – Greenonline Jun 6 '19 at 7:28
  • $\begingroup$ Yes to both. I didn't spend enough time with the schematic. Thank you. $\endgroup$ – cmm Jun 6 '19 at 11:11
  • $\begingroup$ Sorry i didn't put in there that i wanted to use uart for my tmc2208 drivers sorry about that... But are you saying that the chip only expects uart from the usb does that mean i cant use uart for my drivers? $\endgroup$ – lolatron Jun 7 '19 at 2:52
  • $\begingroup$ You can use those pins as you wish, if they are otherwise free. In Arduino, it will be Serial3.begin(baud_rate) to start it. The other port will work as it normally works. $\endgroup$ – cmm Jun 7 '19 at 3:20
  • $\begingroup$ how do i setup the pins.h to tell the Arduino that those pins will be used for uart connections for the stepper drivers? $\endgroup$ – lolatron Jun 7 '19 at 3:43

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