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bigtreetech / BIGTREETECH-SKR-V1.3

32bit board with LPC1768, support marlin2.0 and smoothieware, support lcd2004/12864, On-board TMC2130 SPI interface and TMC2208 UART interface no additional wiring is required
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TMC2209 V1.2 UART Pull Down (R5) needs to be removed #462

Open mkotyk opened 3 years ago

mkotyk commented 3 years ago

Hey all,

I spent WAY too long discovering that using a BTT TMC2209 with a BTT SKR V1.4 just won't work in full read/write mode. The 3.3V pull-up of the gpio against the 20K pull down on the driver board had the UART pin floating all over the place for me.

Screenshot from 2020-11-11 22-01-08

Channel 0 is the modified driver with R5 removed. Channel 1 & 2 are the other axis that are fighting to be high and low.

Everything works fine at 5V when I used an FTDI serial board to test, but then at 3.3V nothing worked.

camnewnham commented 2 years ago

Thanks for posting this @mkotyk . I also just spent way too loo long troubleshooting other components to eventually look up the BTT TMC2209 1.2 schematic and wonder why there's a pull down there.

UART seems to work in TX-only mode but read/write doesn't as you suggested.

Do you happen to have the driver still floating around or any images of it that show the removed resistor? The SMT stencil on mine is pretty blurry and I don't want to accidentally remove the wrong one!

Interestingly, this is also the case on the MSK TMC2209 V2.0 (and V1).

It was not the case on earlier Fysetc boards [2.1](https://wiki.fysetc.com/Silent2209/#v21-hardware-connection and 3.0 but was added in V3.1.

Are most printer mainboards using 5V VIO now? Or do the not use RX? Or am I missing something...