Logic Level shifter for 12864 display on Duet 2 Wifi

[dc42]

I've been working on the code in RRF 3.2 to vary the number of drivers depending on whether a display is configured or not. In the process, I finalised the pin assignments for Duet WiFi to the Fysetc mini 12864 display, as follows.

constexpr Pin EncoderPinB = PortCPin(7);		// connlcd.3	-> exp2.6
constexpr Pin EncoderPinA = PortAPin(8);		// connlcd.4	-> exp2.8
constexpr Pin LcdNeopixelPin = PortDPin(18);       	// connlcd.5	-> exp1.5
constexpr Pin LcdResetPin = PortCPin(28);		// connlcd.6	-> exp1.6
constexpr Pin LcdA0Pin = PortDPin(19);			// connlcd.7	-> exp1.7
constexpr Pin LcdCSPin = PortAPin(25);			// connlcd.8	-> exp1.8
constexpr Pin EncoderPinSw = PortDPin(20);		// connlcd.9	-> exp1.9
constexpr Pin LcdBeepPin = PortDPin(21);		// connlcd.10	-> exp1.10
 
// Additional spi wiring for FYSETC Mini 12864 display:
// connlcd.2 (gnd)	-> exp1.2
// connsd.1 (+5V)	-> exp1.1
// connsd.2 (gnd)	-> exp2.2
// connsd.3 (SD CS)	-> exp2.7
// connsd.4 (sck)	-> exp2.9
// connsd.5 (mosi)	-> exp2.5
// connsd.6 (miso)	-> exp2.10

[jay_s_uk]

Sounds promising. I have one of these displays gathering dust

[Schmart]

Hi @dc42

I've optimized and simplified the code further in my repo and managed to save a few hundred bytes.

Also, the ST7565 display now works without additional logic components, inverting the LCD_CS with a 74xx00 is not necessary anymore. I've used the exp_0 pin for DC and the exp_1 pin for CS now. My display accepts the logic levels perfectly.

I should be able to save another 60 bytes or so, but I have to first work out an issue that I uncovered when I start drawing columns pixel by pixel.

[oliof]

@Schmart where'd one find your patch, and what does the new wiring look like? Inquiring minds want to know ...

[Schmart]

@dc42: I created a pull request of my changes today, and I tested:

• ST7920 display type 1
• ST7565 display type 2 that uses EXP_1 for active low CD
• ST7565 display type 3 which needs a NAND inverter IC to invert the LCD_CS towards the display

Also implemented a couple of optimizations, solved a few bugs and simplified the Flush routine.

I see some room for further size reduction of the firmware, but that would probably make some parts of the code a little slower. What's your stance on that?

[Schmart]

Hi @oliof, back from fishing?

The changes are in the following repo and branch.
https://github.com/SchmartMaker/RepRapFirmware/tree/ST7565

I have a binary firmware for the Maestro here:
https://1drv.ms/u/s!Au1g8fW6BaQzioADewiHDAxzQ_Adlg?e=KuNYOB

What's the board you're using? I'm asking, because the firmware build for the Duet Wifi and Duet Ethernet is still a little too large for the flash memory of these boards unfortunately.

[Schmart]

@oliof I'll see if I can hack the wiring picture so that it reflects the new option that doesn't require the 74xx00.

[oliof]

I have a Duet2Wifi, but I can easily remove stuff I don't need (I did remove Hangprinter when trying the level shifter approach).

[Schmart]

@oliof This is the wiring I used without the inverter.

So to be clear and safe, this is very specific wiring to connect the Duet 2 Maestro to a Creality ST7565-based MiniPanel display @3.3v logic levels.

The pinout of displays made vary wildly, and the connectors on display-side may need to be reversed (the plastic shroud rotated 180 degrees). Also, the firmware adaptations I made in my fork are relatively easy to change for the Duet 2 Wifi, but I believe you would need to make changes in the Pins.h specific to the board and maybe also in Display.cpp (for now).

Edit: Since @oliof is using the exact same Creality MiniPanel display from the CR-20, I have adjusted the diagram to match the exact orientation of the display connectors on that specific display. The tab goes on the side of pin #1.

[oliof]

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

The pinout of displays made vary wildly, and the connectors on display-side may need to be reversed (the plastic shroud rotated 180 degrees). Also, the firmware adaptations I made in my fork are relatively easy to change for the Duet 2 Wifi, but I believe you would need to make changes in the Pins.h specific to the board and maybe also in Display.cpp (for now).

I have a Creality minipanel I want to use, so we're in the clear there. I'll check how Pins.h need to be adapted if I get around to it before this lands in 3.2 or beyond.

[Schmart]

@oliof That would be so cool if you'd get it working as well. I'm not at my computer anymore, but I believe I'm using ‘M918 P2 E4 F2000000‘ in my config.g.

[dc42]

Please note, the wiring diagram posted by @Schmart above is not the wiring arrangement that will be supported in RRF 3.2. The wiring arrangement in 3.2 is listed in this post https://forum.duet3d.com/post/157139.

[Schmart]

@dc42 I saw the post, it wasn't clear to me if this was for the Duet 2 Wifi/Ethernet only or also for the Maestro?

[oliof]

@Schmart I'd assume it will be the same for either.

[dc42]

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

@dc42 I saw the post, it wasn't clear to me if this was for the Duet 2 Wifi/Ethernet only or also for the Maestro?

It's for Duet WiFi/Ethernet. For the Maestro, I chose pin exp.pa21 to connect A0 to (same as in your diagram). To avoid having to invert the CS signal in hardware, I am considering requiring CS of a 7567-based display to be connected to exp.pa22.

[antlob]

@dc42 Can you please confirm if that wire arrangement ( https://forum.duet3d.com/post/157139.) will work not only for the MINI LCD 12864 but also for a standart LCD 12864, mine is a BigtreeTech. Many thanks! If that's the case from lines 11 to 17 I must connect them only if I want the LCD 12864 SD Card support, right? If I prefer the one on the panel due I only need to connect the LCD 12864 to ConnLCD on the Duet 2 Wifi, right?

[antlob]

@antlob Hello! Anybody? Please help!

[oliof]

@antlob I can confirm that the BTT TFT2.4 12864 emulation works on the Duet Maestro which indicates it's an ST7920 and will need a logic level shifter (and a custom firmware build) for the Duet2 Wifi. Unless you share more details about the 12864 you have we cannot give you a straight answer.

[antlob]

@oliof Thanks for the reply. I have the following display . For what I've seen in forums is an ST7920 but don't know how to be certain, the display is soldered to a backplate and don't have access to the chip. So, assuming that I have the correct one, should I follow scheck's diagram? And also seems like I have to compile version RRF 3.02 dev, right? Would it work, in principle? But, if by any chance you already have the *.bin file it would really help me. Many thanks again for your time. My current RRF version is 3.1.1 as suggested by @dc42.

[oliof]

RRF 3.2 only supports the 7565 and 7567 on Duet 2 Wifi by my understanding (I might be wrong there). You need to do Markus Scheck's or @bearer's) diagram.

I don't have the firmware file from my experimentation around anymore, but bearer's code excerpts above should get you going.