Logic Level shifter for 12864 display on Duet 2 Wifi

Schmart

@oliof I'm pretty sure the CR-20 minipanel is based on the ST7565. The first clue was that I haven't been able to find any display modules of that (small) size with an ST7920 on it, they all come equipped with a ST7565. Also, I put a logic analyzer on the display pins of the Creality mainboard, and I'm seeing A0 being actively used as data/command line (4-wire SPI) and the decoded commands correspond to the ST7565 datasheet. Here's a screenshot from a saved capture:

Edit: improved wording.

@Schmart fyi oliof is "gone fishing" for a bit; https://forum.duet3d.com/topic/15792/taking-a-break

Schmart

@bearer Thanks for the heads-up! Then please consider my message as general information for the forum

oliof

Just a little peek to report that I got it almost working with a cloned RepRap Smart Graphics Controller with very low SPI speed (100kHz) and somewhat malfunctioning buttons (stray button presses registered) using a txs0108 -- most likely due to shoddy cabling work.

@Schmart thanks for the headsup. That's a bummer as I lack the time and skill to implement full ST7565 support.

dc42

After a bit more research I discovered that the mini 12864 displays that use the ST7567 chip should already be 3.3V-compatible. That includes this one https://github.com/FYSETC/Mini-12864-Panel and clones, including the Viki 2 and MKS Mini I think. These displays need one more pin that the ST7920-based displays and a modification (probably small) to the driver, but that shouldn't be difficult.

What's stopping me adding this support to the Duet WiFi/Ethernet firmware as standard is that there isn't enough room in flash memory. Recent improvements in RRF 3.01RC and switching to a more recent C++ compiler and library have increased the binary size to 493kb, leaving just 19kb free against 24kb needed.

oliof

ISTR that extra pin is for digital contrast control (the smart full graphics controller has a potentiometer for that) so it might need another option for M918 to set contrast ... likely adding some more memory requirements.

But as long as there's no space in RAM that's likely moot anyways.

dc42

@oliof said in Logic Level shifter for 12864 display on Duet 2 Wifi:

ISTR that extra pin is for digital contrast control (the smart full graphics controller has a potentiometer for that) so it might need another option for M918 to set contrast ... likely adding some more memory requirements.

It's not for contrast control, it's just that the ST7567 controller chip needs a command/data input pin as well as data, clock and CS.

oliof

Today I learned.
That said, I'd be willing to carry a patch removing unnecessary kinematics for an unofficial unsupported build with ST7567 support to make space -- I already know how to do that. I should be able to keep the patch going in case it needs changes ...

@dc42 I want to thank you a lot for even putting forward the consideration of including it; I also understand other features would be prioritized indefinitely.

antlob

@oliof @dc42 @bearer

First of all congratulations for the great job, I'm new to Duet 2 Wifi and have an LCD 12864 that came with my 3d printer (secKit Go) I also have the Paneldue 4,3". My first question is: Could I have both displays working at the same time? If I loose the SD card on the LCD 12864 would be fine since I have it on the Paneldue 4,3". What I would really like is to have the encoder operational on the LCD 12864. Is this doable? Many thanks in advance for your support.

oliof

emerges from time spent away from 3d printing

If the SecKit go panel is driven by an ST7920 it will work with the level shifter and a custom Duet2 Wifi firmware that makes space for the LCD12864 support today by cutting something else (for example a motion system you don't need on your printer like Hangprinter).

AFAICS using an LCD12864 and PanelDue in parallel works. But then v3 PanelDues have the pins for an encoder and there will be support for it in a future release so maybe it's better to wait for that.

submerges again

antlob

@oliof said in Logic Level shifter for 12864 display on Duet 2 Wifi:

v3 PanelDues

Thanks @oliof for the reply. It does have the ST7920 so I I would need to connect the LCD to the CONN LCD on the Duet and add a level shifter following the schematics on the forum above skipping the SD Connector, rigth?. That does not seem hard but, my struggle is with the firmware, following Markus Scheck blog and the comments above in the fourm there are some libraries to be included and minor changes to be made to them. I've found this instructions for building https://github.com/Duet3D/RepRapFirmware/blob/dev/BuildInstructions.md of the @dc42 fork but ... I know it is a stupid question and sorry in advance, Where can I find the source libraries to make the bin file? My current version on the Duet 2 Wifi is 2.05.

Thanks again for your time.

@antlob Looks like they've started migrating to https://github.com/Duet3D/

btw, you need the gate function of the 7408 as well as its level shifting. (I used the TXS0108 as the enable pin mimicked the AND gate function.

antlob

Thanks for the tip @bearer, found them finally, is huge but I'll definitely try it. Just one question, if I only connect ENC_SW, ENC_A, ENC_B, BEEP on the Duet 2 CON_LCD to the EXP 1 and EXP 2 on the LCD 12864. Will it work? The CON_SD is used right know to support the SD on the PanelDue.

@antlob said in Logic Level shifter for 12864 display on Duet 2 Wifi:

Will it work? The CON_SD is used right know to support the SD on the PanelDue.

CON_SD is also needed to drive the display, it uses the SPI bus for both, which is why I opted to change things around so I could connect only CON_SD and have a functional display sans the encoder.

antlob

OK! So for what you say it is impossible to connect this LCD only from CON_LCD. I do not have the required knowledge to swap the SPI pins to CON_LCD, or maybe it is not even possible. Thank you, you saved me a lot of time!

@antlob said in Logic Level shifter for 12864 display on Duet 2 Wifi:

me the modified libraries to make the build?

I didn't modify any libraries, and the patch against RRF is up there somewhere, and I believe we included it on the easyeda page for the board as well.

I don't have access to the computer I built the firmware atm, but i found these locally, if you're prepared to recover by usb/bossa you could give it a try.

https://www.dropbox.com/s/g42b7gye964sd5e/Duet2CombinedFirmware_2.0.51_LCD8.bin?dl=1
https://www.dropbox.com/s/f7fjuu7f0wcf7dc/Duet2CombinedFirmware-rrf3-lcd.bin?dl=1

dc42

The RRF v3.02-dev branch now includes the changes needed to support ST7920 and ST7567 displays in the source code. Unfortunately the generated binary is too large if you enable SUPPORT_12864_LCD in the standard Duet2CombinedFirmware build. So something else will need to be done, perhaps one of the following:

Strip out unused functionality
Use separate builds for Duet Wifi and Duet Ethernet, so that only one set of network code is needed
Remove the large font
Change the optimisation options to optimise for space instead of speed, and use function-specific attributes on those functions where optimisation for speed is desirable

antlob

@bearer Many thanks! I'll make the circuit on a breadboard just to see if I can turn on the display.

antlob

@dc42 Many thanks for replying. In my case would be to build just for the Duet Wifi and discard the Ethernet but my concern really is that in order for me to use LCD 12864 I would need to sacrifice the SD card support on the Duetpanel and maybe the SD on the LCD 12864 cannot be read by the DWC. If by any chance I could read the card on the LCD panel then I would go for it but as you say a separate build for the Wifi and Ethernet should be made and I don't know how to do it.

dc42

@antlob said in Logic Level shifter for 12864 display on Duet 2 Wifi:

@dc42 Many thanks for replying. In my case would be to build just for the Duet Wifi and discard the Ethernet but my concern really is that in order for me to use LCD 12864 I would need to sacrifice the SD card support on the Duetpanel and maybe the SD on the LCD 12864 cannot be read by the DWC. If by any chance I could read the card on the LCD panel then I would go for it but as you say a separate build for the Wifi and Ethernet should be made and I don't know how to do it.

I've changed the compiler options in the Duet2Combined build of RRF 3.02 to optimise for space instead of speed, and saved some space in a few other places, and it now fits. Sometime soon I will change it to include the 12864 support as standard and automatically disable the extra 2 stepper drivers if the display is enabled using M918. I haven't yet assigned the extra pin needed by 12864 displays with ST7567 controllers, or the extra pin needed for backlight control on some displays, but I plan to take those from CONN_LCD too - which is why I will disable both stepper drivers on the connector.