12864 display (ST7920) on Duet 3 Mini5+

DIY-O-Sphere · 5 May 2021, 20:20

I have connected a level shifter to the Duet Mini+.
In principle, the display works, the printer can be operated, but there may be an error in my circuit since strange artefacts are visible.

I have orientated myself on this.
But it took some time to work through the thread, because it ends up being a mishmash of different firmware, boards and lcd types.

I tried to create a mapping table between the maestro and the mini, because the display ran perfectly on the maestro before.
Since the names and functions of the pins are differently, it was difficult to create the circuit diagram.
The pins that I could not clearly assign are marked in red. This is where I suspect the issue.

Edit:
Wiring schematic updated to the fully functional revision

DIY-O-Sphere · 5 Jan 2021, 19:25

I now have reduced the frequence in M918 and the artefacts are gone.
Does that mean that the shifting isn't working?

pixelpieper · 1 May 2021, 19:29

@diy-o-sphere it just means that your level shifting circuit isn’t fast enough for stable operation. If it works with the reduced frequency you are fine.

DIY-O-Sphere · 1 May 2021, 19:35

@pixelpieper
Reducing 1Hz does the trick...
M918 P1 E-4 F1999999 works....

pixelpieper · 1 May 2021, 19:39

@diy-o-sphere I would change it by more - maybe half the default. Otherwise this might break again with small environmental changes in temperature or humidity or just over time...

alankilian · 1 May 2021, 19:47

@diy-o-sphere Do you have the data sheet for your LCD module?

I looked at several and found the maximum SPI clock to be between 800,000 Hz and 2,500,000 Hz so it looks like the modules are quite different from one another.

DIY-O-Sphere · 1 May 2021, 19:59

@alankilian
No. It is a cheap clone which I had bought when I had started with the Ramps,
But it worked propper for years on the Maestro (2Mhz)
The circuit is still sitting on the breadboard, the "cable spaghetti" is certainly not very helpful.

DIY-O-Sphere · 4 May 2021, 21:11

@dc42
Can you please take a short look at the wiring diagram?
The LCD works fine now, but I can't get the SD card reader to work.
My best guess is, it has someting to do with SPI2_CS0 on the output.
I already tried connecting to SPI2_CD and SPI2_CS3, but no success.
(I don't use the external SD Card, but I would like to have the wiring right.)

dc42 · 5 May 2021, 07:52

@DIY-O-Sphere, are you really saying that the LCD works if you use F1999999 in the M918 command, but not if you use F2000000 ? That sounds most unlikely.

Three comments:

The level shifter IC should be 74HCT08, not 74HC08.
You should ground the unused 1A and 1B inputs of the 74HCT08, or connect them to +5V.
The Duet 3 Mini has a card detect input, SPI2_CD in your diagram. You should connect that to the card detect output of your LCD if it has one. It's probably EXP2 pin 7 on your LCD. Caution, you must not apply 5V to SPI2_CD. So check that EXP2 pin 7 is connected to ground when the SD card is inserted, and is floating when it is not. If the LCD doesn't support the card detect output, ground the SPI2_CD pin instead.

HTH David

DIY-O-Sphere · 5 May 2021, 16:37

@dc42 said in 12864 display (ST7920) on Duet 3 Mini5+:

The level shifter IC should be 74HCT08, not 74HC08.

It's a typo IC is 74HCT08

You should ground the unused 1A and 1B inputs of the 74HCT08, or connect them to +5V.

I will do this later in a soldered pcb board

The Duet 3 Mini has a card detect input, SPI2_CD in your diagram. You should connect ............

You are briliant
It is not shown in the diagram but it is present. (The Maestro didn't have the connector).
When the card is inserted it changes from 0.4V to 0V. I think that should be fine.
I have currently connected SPI2_CD to ground and it works.
Thanks a lot.

I still have one final question.
I have an accelerometer that I want to connect to the PanelDue connector.

Will this work in combination with the LCD sd card reader (same SPI bus)?
I will not run both at the same time.

dc42 · 5 May 2021, 18:56

@diy-o-sphere the accelerometer is normally connected to the temperature daughter board connector. I think it should be possible to use the PanelDue connector instead, but I haven't tested that. It should work OK with the LCD card reader if the cables are short.

DIY-O-Sphere · 5 May 2021, 18:15

@dc42

the accelerometer is normally connected to the temperature daughter board connector.

My pIan was, that by using IO.0 only one plug is required.
But it's just to play around.
I will buy the new toolboard as soon as it is available here.
Thanks for the announcement
I don't feel disadvantaged, quite the opposite.

PCR · 17 Jun 2021, 15:12

Hello i am in the process of making a small Production run based on @DIY-O-Sphere schematic. IT will be Board which will be directly olugged Into the Mini;)
Please upvote If you want one!