I'm using a Pico in my project, I run the tube driving routine on one core and everything else on the rest so it doesn't suffer from slowdowns. I've had to introduce a delay to slow it down to a 1ms refresh!
Craig On Wednesday, 1 November 2023 at 15:47:33 UTC gregebert wrote: > Multiplexing might not be possible in certain software environments. > Several years ago I switched to Linux-based Raspberry Pi systems in my > projects, and with the unpredictable overhead of Linux I cant rely on the > CPU being available every millisecond to update the display. Instead of > using Arduino or a custom OS, I add an FPGA or CPLD to handle the time- > critical tasks. > > Just by coincidence, I'm putting the final touches on the software and RTL > code for a board I recently had fabbed to do this. I know it's blasphemy, > but the first project using this is LED-based...I got a bunch of large 8x8 > red/green LED arrays for just under 1 USD apiece and the need a multiplexed > driver. Dont worry, there are several nixie and nixie-ish projects in the > pipeline that will use this board. > > > [image: raspi_fpga.JPG] > > On Wednesday, November 1, 2023 at 8:19:48 AM UTC-7 Richard Scales wrote: > >> @Paul - I have no idea of the sense of scale and the relative times >> taken. If I were to hang another HV driver on the chain with associated >> electronics to switch the HV, is there going to be enough time to do the >> following: >> >> Set the bits for the segments required- I add this step just in case any >> settling time might be be required >> Set the bits for the segments required and the anode(s) on >> Wait for 400us (typical on time for the panaplex segments I have in mind >> Set the digits and anode(s) off again >> Loop to the next set of digits >> >> With 12 individual anodes - there would be 12 passes - one for each anode >> that needed to be switched on >> If I used 2 drivers (using 3 x 16 bits for cathodes, I could use bits >> from the remaining 16 to control the anodes. Thus there would be only 3 >> passes. >> >> Please stop me when I've gone off the scent (still mid-covid) :-( >> >> In Summary: >> Using the HV55xx for cathodes AND anodes >> Given i want 12 characters: >> with 1 driver I have 16 segments and 16 spare for the 12 anodes - easy >> but slowest >> with 2 drivers I have 3 lots of 16 segments and then group the displays >> into lumps of 4 (12 characters/3) and still have 16 bits to control the >> anodes, of which there will now only be 3) >> >> Am I anywhere near close with the driver split and the pseudocode for the >> ISR? >> I was thinking that there should be some uS delays either before and/or >> after lighting the segments >> >> >> - Richard >> >> >> On Wednesday, 1 November 2023 at 15:01:20 UTC Richard Scales wrote: >> >>> @David - many thanks for that caution though there will not be (nor ever >>> will there be!) any LEDS for this project! >>> @Pauld - thank you - I had thought of that but I was endeavouring to >>> keep the code inside the ISR to an absolute minimum so thought that it >>> would be best handled outside of it and hence separate from the HV chain. >>> Using SPI.Transfer to send 32, 64 or 96 bits - I guess it all happens >>> fairly quickly! >>> @Benoit - I will look at that - ESP32 - another bridge thus far >>> uncrossed! >>> - Richard >>> >>> >>> On Wednesday, 1 November 2023 at 14:54:53 UTC Benoit Tourret wrote: >>> >>>> Hello, >>>> >>>> if an ESP8266 is not enough powerful, the ESP32 will do the job. >>>> the ESP_WROVER can be a good platfom. >>>> you should have a look to Mose's work on >>>> https://neonixie.com/Z57XM6DV2/ >>>> the code is a bit "strong" as it can be used both on an 6 IV-9 clock >>>> and a more traditional 6 digits Z57, superb clocks, all they need is >>>> addressable LEDs for a more colorful background. and deactivable. >>>> the BH1750 luxmeter does a great job and is more sensible than a >>>> standard photoresistor. >>>> >>>> Le mercredi 1 novembre 2023 à 14:38:44 UTC+1, David Pye a écrit : >>>> >>>>> Hi, >>>>> >>>>> I offer you one caution with the ESP8266 boards - almost everything is >>>>> implemented in the libraries in software rather than onchip hw. >>>>> >>>>> That means doing things like updating addressable LEDs can cause the >>>>> multiplexing to glitch slightly because of the need to send LED data at >>>>> strict timings. (Or, if you sacrifice led timings to run your multiplex >>>>> interrupt routine, it can glitch the LEDs. ). Chips which have DMA/more >>>>> complex peripherals might avoid this. >>>>> >>>>> You might get away with it with certain combinations of things but it >>>>> was a bit of a pain for me. >>>>> >>>>> David >>>>> >>>>> On Wed, 1 Nov 2023, 11:54 Richard Scales, <[email protected]> >>>>> wrote: >>>>> >>>>>> Many thanks Nick. >>>>>> Unless anything else comes to light I think I will forge ahead on >>>>>> that basis. I want to drive 15 segment panaplex displays (16 including >>>>>> the >>>>>> DP) so plan to use HV5530 or similar driver for the segments, probably >>>>>> two >>>>>> of them. Then the same MPSA42/MPSA92 driver arrangement for the HV >>>>>> though >>>>>> there are going to be 5 of those - I might be running low on pins it >>>>>> using >>>>>> a Wemos - I might consider a port expander for the extra pins needed - I >>>>>> need to check pins required - I think 4 for the HV register chain, 6 for >>>>>> the Anode switching (two drivers driving a 12 digit device - perhaps 5 >>>>>> for >>>>>> a 10 digit device) plus I want to read a PIR and talk to a BMP-280 >>>>>> sensor. >>>>>> Certainly a Wemos + port expander would do it - might get away with a >>>>>> Node >>>>>> MCU or similar. >>>>>> OK, I just realised that I can use a single 32 bit driver with two >>>>>> sets of 16 bits, one going to each bank of displays. >>>>>> It still has the same pin requirements of the processor I think. That >>>>>> will be a juggling excersise! >>>>>> - Richard >>>>>> >>>>>> >>>>>> On Wednesday, 1 November 2023 at 11:10:02 UTC Nick Sargeant wrote: >>>>>> >>>>>>> Hi, >>>>>>> >>>>>>> It’s not difficult. My fumbling attempts at a Nixie clock some time >>>>>>> ago used a 4:1 multiplex ratio, using four digits and only one decoder. >>>>>>> I >>>>>>> used the same MPSA42/MPSA92 driver as your example. My multiplex >>>>>>> function >>>>>>> was called at 100Hz, so each digit was refreshing at 25Hz. It doesn’t >>>>>>> flicker, and (whoa!) it is working 15 years later. >>>>>>> >>>>>>> The only mod I had was when switching between digits, I turned the >>>>>>> cathode drive off for a period of 20 microseconds, before selecting the >>>>>>> correct anode and turning on the next digit. This helped prevent >>>>>>> ghosting. >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Wednesday, 1 November 2023 at 10:14:25 UTC Richard Scales wrote: >>>>>>> >>>>>>>> Actually - I just looked through an example over at: >>>>>>>> https://www.hackster.io/doug-domke/multiplexed-nixie-tube-clock-759ff5 >>>>>>>> >>>>>>>> ... and it all seems fairly understandable, have I overthought this? >>>>>>>> >>>>>>>> - Richard >>>>>>>> >>>>>>>> >>>>>>>> On Wednesday, 1 November 2023 at 09:22:03 UTC Richard Scales wrote: >>>>>>>> >>>>>>>>> The time has come when I need to get a handle the dark and >>>>>>>>> mysterious art of multiplexing. >>>>>>>>> I have an understanding of what needs to happen though am mostly >>>>>>>>> at a loss of how to implement it. >>>>>>>>> I am broadly assuming that I should be using some kind of >>>>>>>>> interrupt routine to make the actual display work whilst the rest of >>>>>>>>> the >>>>>>>>> code gets on with the job of working out what to display and when to >>>>>>>>> display it. >>>>>>>>> Is it even going to be feasible to have some kind of interrupt >>>>>>>>> routine that decides what digits to light - set all the bits and then >>>>>>>>> sets >>>>>>>>> the right anode(s) on and then off again giving enough time for the >>>>>>>>> persistence of vision to produce a non flickering display when using >>>>>>>>> something like a wemos D1? >>>>>>>>> >>>>>>>>> I am thinking that the interrupt routine needs to increment which >>>>>>>>> digit(s) is/are being illuminated - set up the right bit pattern for >>>>>>>>> the >>>>>>>>> cathodes and turn on the relevant anode(s) - wait a little and then >>>>>>>>> turn >>>>>>>>> them off again. >>>>>>>>> My worry is that the amount of time that the displays should be >>>>>>>>> left on might be a little too long for the ISR as my understanding is >>>>>>>>> that >>>>>>>>> these should be kept as lean as possible. >>>>>>>>> >>>>>>>>> Do I even need multiple interrupts (my covid addled brain is >>>>>>>>> struggling to type let alone contemplate multiple ISR's!)? >>>>>>>>> Can the rest of my code run in a non time critical manner as it >>>>>>>>> works out what it wants to display where whilst the interrupt routine >>>>>>>>> merryly illuminates digits based on values which I store in a buffer >>>>>>>>> somewhere? >>>>>>>>> ... or does the rest of my code have to work in come kind of >>>>>>>>> state-machine fashion? >>>>>>>>> I would expect (hope) to handle display brightness via PWM signals >>>>>>>>> to HV Drivers. >>>>>>>>> I have no need for cross fade effects either - just basic >>>>>>>>> multiplexing of say 10 different multi segment displays. I am more >>>>>>>>> than >>>>>>>>> happy to break up the displays into say 2 (or more) groups in order >>>>>>>>> to >>>>>>>>> makes things a little easier. >>>>>>>>> >>>>>>>>> Can anyone point me in the right direction - ideally with some >>>>>>>>> code snippets that I can use as a foundation? >>>>>>>>> >>>>>>>>> Just to confirm, it is only the general implementation to drive >>>>>>>>> the displays that eludes me - the rest of the clock code is well >>>>>>>>> defined >>>>>>>>> and working well in a direct drive capacity. >>>>>>>>> >>>>>>>>> The desire to move to multiplexed operation is born out the the >>>>>>>>> desire to drive a greater number of displays with a greater number of >>>>>>>>> segments which could be done via direct drive but I foresee that >>>>>>>>> multiplexing the displays will simplify the electronics required. >>>>>>>>> >>>>>>>>> So many questions I know. I would be grateful for any pointers, >>>>>>>>> thank you. >>>>>>>>> >>>>>>>>> - Richard >>>>>>>>> >>>>>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "neonixie-l" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>> send an email to [email protected]. >>>>>> To view this discussion on the web, visit >>>>>> https://groups.google.com/d/msgid/neonixie-l/e576bff1-8d65-4d53-b0cc-2ba5ba574232n%40googlegroups.com >>>>>> >>>>>> <https://groups.google.com/d/msgid/neonixie-l/e576bff1-8d65-4d53-b0cc-2ba5ba574232n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> >>>>> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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