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Forum Index : Microcontroller and PC projects : controlling 6 LCD displays with 1 PicoMite
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| ville56 Guru  Joined: 08/06/2022 Location: AustriaPosts: 405 |
I'v managed to control 6 LCD displays based on ST7789 to simulate good ole Nixie tubes. This is done by simply de-muxing the CS signal for each display, all other singnals are tied as a bus. The only odd thing is that the reset line must not be connected to the Pico, just left open or high. Init is done by selecting the individual displays CS and issuing GUI RESET LCDPANEL. After that just select the required LCD CS and display the content. Have to let it run for a while now, just to see if there are issues ....  73 de OE1HGA, Gerald |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3620 |
Retro to the max. Congrats. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8578 |
A thing of true beauty! I take my virtual hat off to you sir. :) If you are going to make things complicated then this is truly the way. Congratulations. lol . Edited 2026-02-20 02:09 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| ville56 Guru Joined: 08/06/2022 Location: AustriaPosts: 405 |
Thank you. I've never been easy and I've always known how to get simple things done the hard way.  73 de OE1HGA, Gerald |
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rrroonn Newbie  Joined: 08/02/2026 Location: AustraliaPosts: 8 |
Wow. Impressive. If all else fails, remain flexible and maintain a sense of humour |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2494 |
that is really impressive  where abouts exactly did you source the LCDs? i'm inclined to have a go myself. cheers, rob :-) |
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| ville56 Guru Joined: 08/06/2022 Location: AustriaPosts: 405 |
The displays are from Aliexpress, but they are available from many of the usual sources and they all seem to be the same. Only the price differs a lot. See if they have the ST7789 controller on board. I've only tested this controller to work in the multiplexed setup. As demux decoder I use a 74HC138 for the CS signals. On thing to consider also is, the display has a geometry of 320x160 pixel, but the small side (160px) has an offset of 35, so the coordinate range is from 0,35 to 320,195. Otherwise there is no difference. The MMBasic driver I use is ST7789_320 in portrait mode. To load the images I use BLIT LOAD / BLIT WRITE / BLIT CLOSE for speed reasons. Preloading the 10 images into BLIT buffers, which would have been even faster, did not work, it caused hangs if more than 3 buffers were used. And important, leave the RESET signal of the displays unconnected or tied to HIGH. With reset connected to the signal from the pico it doesn't work. Seems as the controller does listen to RESET even if his CS is inactive. So maybe to be on the safe side RESET could be asserted by an extra output pin at startup. Didn't and have no issues so far. My display board is a rats nest created with Vero wire, so my initial fear of having distorted CLK and SDA was unneccessary. The other signals are more or less "slowly moving DC" and have not been of concern to me. I've also played around with ST7735S controllers/displays some time ago. They also worked in a similar setup but I've considered them as to be too small for makeing a usable clock. Source Link  73 de OE1HGA, Gerald |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8578 |
Well, you can't get nixie tubes at that price any more. :( Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 5713 |
Volhout PicomiteVGA PETSCII ROBOTS |
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| ville56 Guru Joined: 08/06/2022 Location: AustriaPosts: 405 |
If someone is interested in the Nixie bmp/jpg files I can upload them here. It is from a Z5680M tube. Found them on the web (danyk.cz) and adapted/resized/recolored them, and they are freely available if in accordance to the statements on his web page (adding your own stuff and mentioning his website danyk.cz). 73 de OE1HGA, Gerald |
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| bfwolf Senior Member  Joined: 03/01/2025 Location: GermanyPosts: 173 |
You can make even the simplest thing arbitrarily complicated... But yes: It's quite possible that all six LCDs, including the backlight, consume less energy than one Nixie tube. I think they're hard to find these days anyway? From Russia?  |
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| ville56 Guru Joined: 08/06/2022 Location: AustriaPosts: 405 |
Power saving is not really possible with it ... a Nixie consumed about 500 to 800 mW per digit. This is quite comparable with a small LCD display with background light. It's the voltage that is more comfortable to work with. I remember being bitten by the 150V a number of times when I was servicing equipment with Nixie displays. But that is long time ago. Now I've changed my clock display to ET1 tubes, a genious tube design. Makes it much harder to figure out how late it is ....  but you can even see the filament glow.73 de OE1HGA, Gerald |
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PeteCotton Guru Joined: 13/08/2020 Location: CanadaPosts: 606 |
Absolutely brilliant! |
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| Bleep Guru Joined: 09/01/2022 Location: United KingdomPosts: 734 |
Hi Gerald, I already have several genuine IN-12 Nixie clocks, I bought the tubes about 10 years ago, luckily they seem reasonably reliable, but why not make a Pico Nixie clock as well, so yes please to the Nixie images. Regards Kevin. |
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| ville56 Guru Joined: 08/06/2022 Location: AustriaPosts: 405 |
Kevin, here you go Z5680M-BMP.zip Z5680M-JPG.zip The images are tailored for the 320x170 displays, 16 colors. Edited 2026-02-21 08:23 by ville56 73 de OE1HGA, Gerald |
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| bfwolf Senior Member Joined: 03/01/2025 Location: GermanyPosts: 173 |
"Electricity might hurt".. |
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| v.lenzer Regular Member  Joined: 04/05/2024 Location: GermanyPosts: 98 |
Hi Gerald! A truly unique project. Simply ingenious! Would you be willing to publish the source code? I've already ordered the displays (the price is very reasonable). The circuit itself shouldn't be too complex. However, I have a question about the picture you posted. I see power LEDs behind the "Nixie tubes." Is that related to your circuit (backlighting)? I'm currently loading your Nixie digit images from an SD card every second and displaying them on a 320x240 display. Just to see how it looks. And I have to say: it's really realistic. Best wishes! Joachim |
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| ville56 Guru Joined: 08/06/2022 Location: AustriaPosts: 405 |
Hi Joachim, sure I can post the source but I'm far from finished. So far it only displays the result of TIME$ every second, no RTC module, no DCF77, no GPS or NTP access and the comments need some enhancements too to make it readable. Currently I'm tinkering with a 3D printout for masking the displays and colons. The mechanics part is always the hardest part for me. My plan is to have it running on a WebMite 2 using the NTP service. Same as my kitchen clock I built some time ago. Currently it runs on a WeACt RP2350B module for development, but changeing it to WebMite with NTP should be easy given I don't run into other problems like memory or so which I do not expect at the moment. The LEDs you see are WS2812B strips with 10 leds on it for the colons. Wanted to make the blinking colons as close as possible to the colors of the nixie tubes. The problem is that the leds are much too bright compared with the LCD displays and dimming the down to an acceptable level did result in disturbed color impression. Was thinking about masking them with a (grey) filter but did not find something in my pool of fancy stuff yet. So I changed to simple yellow leds for the colons for now, with PWM brightness control. But they are still interchangeable with the WS2812 as all display stuff is mounted on a socket row and the code for them is still in. If you want the circuit I'm using I can post a scan of my schematic after I've updated it. And yes, it's quite simple just the 74HC138 for the CS signal. This would also match the the code then (pin-numbers in the code and signals in the HW). 73 de OE1HGA, Gerald |
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