Using RA8875 driver + tft on marlin

Hi,

I would like to ask your expertise/advise on this:
I want to add a adafruit RA8875 driver with tft screen to my printer (for this instance the ultimaker electronics) this board uses spi for communication.
Now what i would like is that i can use the EXT1 and EXT2 port to handle communications, i will have a seperate sd reader and potmeter which will also hook up to EXT1/EXT2 (to the corresponding pins).
The question about this is: Does the sd reader use spi too? or does this use tx/rx? what would i have to do to make this work? of course i can program the tft to respond to the data which is already sent to the display.
I hope you can help me, and for more info please ask me, since i might not be explaining this enough.

With kind regards,

Raymond/Napalm1432

SD card uses SPI, its the protocol that the SD card talks, the interface is normally just voltage level shifting (SD card is 3.3v)

You can in theory daisy chain SP devices as long as they support high impedance mode. (no idea if they do or not)

SPI is part hardware, you have to use MISO, MOSI and SCK pins on EXT2 The 4th pin is the SS line, which is really a device select line and can be any IO line. One unique IO select line per device.

Edited 3 time(s). Last edit at 01/27/2016 04:39AM by Dust.

Thank you for clearing this up!

I was also thinking of making a seperate controller, with a seperate arduino (sd reader and potmeter built in(maybe opening for usb stick of possible??)) so you can just hook it up with usb to control
any printer.

Quote
Napalm1432
I was also thinking of making a seperate controller, with a seperate arduino (sd reader and potmeter built in(maybe opening for usb stick of possible??)) so you can just hook it up with usb to control
any printer.

You mean like PanelDue?



PanelDue uses a serial link to the printer, so the USB port is still available for connecting a PC. It's already supported by RepRapFirmware and Repetier, and Smoothieware support is being written.

Driving a dumb TFT panel over SPI is not advisable. Even a low res mono graphics LCD such as a 12864 places a substantial load on the the main processor. Colour TFTs have higher resolution and typically 16 bits of colour information that need to be passed, so the load is very much higher. That's why PanelDue has an ARM-core processor on board.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].