Functionality of Direction Pin

vanvught / rpidmx512

Orange Pi DMX512 / RDM / MIDI / OSC / Art-Net / WS28xx / L6470 / Stepper / TLC59711 / PCA9685 / Servo / PWM / TCNet / SMPTE / RDMNet / LLRP / GD32 / GigaDevice / Raspberry Pi

http://www.orangepi-dmx.org/

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Functionality of Direction Pin #279

Open pilo1337 opened 10 months ago

pilo1337 commented 10 months ago

Hi,

it seems that i dont have understood the functionality of the data direction pin. i connected a MAX485 with RE&DE shorted together to the data direction pin. but i only get dmx out, no in.

what am i doing wrong?

vanvught commented 10 months ago

The H2+ ARM SoC has 3V3 GPIO pins. The pull-ups should be connected to 3V3 -> A quick fix could be removing all the pull-ups.

The MAX485 VCC should also be at 3V3. But that is not working according to the datasheet.

A level-shifter could be a better solution.

Schermafbeelding 2023-10-17 om 20 15 57

Or alternatively C428880 Schermafbeelding 2023-10-17 om 20 17 05

pilo1337 commented 10 months ago

oof, never thought about the 3v3 gpio pins.. my mistake.. there will be a rs485 bus driver with 3v3 supply voltage, i change the board either to another driver or add a level shifter.

thank you!

pilo1337 commented 10 months ago

can you tell me if this should work? i use the max3485 now, which is a 3v3 rs485 bus driver: https://www.mouser.de/datasheet/2/256/MAX3483E_MAX3491E-1291288.pdf