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Forum Index : Microcontroller and PC projects : RP2350 HDMI with 720P goodness
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| Exile Newbie  Joined: 27/05/2023 Location: United KingdomPosts: 6 |
I've successfully run the CVT-RB (320MHz) and CVT-RBv2 (300MHz) timings on my Pico2 in an Olimex board running the SDK dvi_out_hstx_encoder example and got a valid display on the monitors and TVs that I tried. On my Pico2 300Mhz works at 1.1V, 320MHz requires 1.2V. I guess the question is whether there is enough CPU time on the second core to process the overlays etc for 720p at the lower clock rate? |
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| matherp Guru  Joined: 11/12/2012 Location: United KingdomPosts: 9105 |
Did you use the vsync/hsync directions in the posted list? I tried the 320 and got nothing and the non-RB version disagrees with the spec I found https://projectf.io/posts/video-timings-vga-720p-1080p/ |
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| Exile Newbie Joined: 27/05/2023 Location: United KingdomPosts: 6 |
I think the values in the link you provided correspond to the CEA-861 line in the link I provided. The polarity is the same for these. I've attached a zip of the updated dvi_out_hstx_encoder.c file from the Pico SDK that I used with the Olimex board. The defines in lines 42 to 45 determine which video mode is built. All of the modes display on on my monitors, but that is not a very large sample size  The 640x480 mode in the original SDK file corresponds to the 640x480 mode in the link I gave for CEA-861. The polarity matches (both negative) dvi_out_hstx_encoder.zip |
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Sasquatch Guru Joined: 08/05/2020 Location: United StatesPosts: 362 |
Please note: I am not reporting this as a "bug" or "flaw" or something to be fixed. Just thought I'd report on some testing in case it's helpful or may save someone some agrivation. I am having mixed results with the widescreen modes (720P) I have tested on 5 HDMI TV's so far. I have one 24" Vizio branded TV that will properly display a nice edge-to-edge picture in 720P mode. However, the TV seems to lose sync every few minutes and go blank. Almost immediately, it will regain the signal and briefly display the OSD indicating a 720P signal, and then resume displaying properly. I thought perhaps I had a connection problem somewhere, but the exact same setup works perfectly at 640X480 The other 5 TV's I have tested (from 13"-55") won't display the widescreen (720P) image properly. 4 of them won't display anything, as though no signal was connected, and the other will display an image with lots of banding and "snow" similar to the image @homa posted near the beginning of this thread. All of the tested TV's work great with HDMI at 640X480 with a nice stable image provided that +5V is connected to the Adafruit HDMI breakout board. I tested with a DELL branded computer monitor using a passive HDMI to DVI cable. The monitor will only sync to the signal occasionally and even then there is a narrow blue stripe down the left hand side, the image is offset, and the image quality is poor. Also the auto-size feature of the monitor does not seem to detect a valid signal when the auto-detect button is pressed. This monitor and cable also work perfectly at 640X480 It would seem that the 720P mode being used is not fully supported or "standard" for HDMI TV's (at least here in the US???) Your Mileage May Vary. As always I am willing to re-test if there are potential tweaks to the signal timing etc. PicoMiteHDMI MMBasic Version 6.00.00b6 OPTION FLASH SIZE 16777216 OPTION KEYBOARD US OPTION PICO OFF OPTION CPUSPEED (KHz) 372000 OPTION DISPLAY 45, 80 OPTION WIDESCREEN ENABLE OPTION SDCARD GP5, GP2, GP3, GP4 OPTION PLATFORM HDMIbasic OPTION DEFAULT FONT 3, 1 Edited 2024-09-12 03:48 by Sasquatch -Carl |
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| Bleep Guru Joined: 09/01/2022 Location: United KingdomPosts: 509 |
I have found exactly the same, so you are not alone. :-) To be honest I'm not at all bothered with 720p, because of it's different aspect ratio to all the existing modes, it's only minor advantage is to getting the overall clock speed higher. post in 2350 firmware Edited 2024-09-12 05:22 by Bleep |
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stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2120 |
> option list PicoMiteHDMI MMBasic Version 6.00.00b6 OPTION AUTORUN ON OPTION FLASH SIZE 4194304 OPTION KEYBOARD UK OPTION CPUSPEED (KHz) 315000 OPTION DISPLAY 30, 53 OPTION HDMI PINS 1, 3, 7, 5 OPTION SDCARD GP22, GP6, GP7, GP4 OPTION AUDIO GP26,GP27', ON PWM CHANNEL 5 OPTION MODBUFF ENABLE 192 OPTION PLATFORM OLIMEX > this is my olimex and pico2 hdmi works hdmi to old luxor tv |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2120 |
RUN [105] Play modfile "b:\sfx-bg.mod" '"RISsound.mod" Error : Not enough memory >  |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9105 |
You are in mode 3 so a framebuffer takes 640x480x4-bits = 153K. Playing a mod file requires buffers for playback so you ran out of memory - this is just a simple limitation of what memory is available |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2120 |
thanks sir. I'm dim. I thought you was doin magic with memory .a nostalgia chip? na serious all amazing . can be a ott sometimes but not moanin. the olimex is cool."for a pcb" . but how long before something else? |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2120 |
' Bubble Universe mode 3 option autorun on Dim Float u,a,p,q,t,v=0, x=0 Dim Integer g,b,i,j,c(41),d(41),e(41),n(41) Dim Integer f(41,41),l(41,41),m(41,41) Const w=MM.HRes/2, h=MM.VRes/2 Const r=(2*Pi)/235, o=h/2 FRAMEBUFFER CREATE F FRAMEBUFFER WRITE f CLS RGB(black)':Backlight 95 t=Rnd*10:math set 2,e()'Math set 3,e() For g=0 to 41 for b=0 to 41 m(g,b)=rgb(g*6,b*6,128*(g+b>30)*(g+b<60)) Next:Next Do Inc t,0.025:g=0:Timer =0 For i=50 To 255 Step 5 b=0 a=r*i Math Slice f(),g,,c() Math Slice l(),g,,d() Box c(),d(),e(),e(),0,,0 For j=50 To 255 Step 5 p=i+v:q=a+x u=Sin(p)+Sin(q):v=Cos(p)+Cos(q) x=u+t:c(b)=w+u*o:d(b)=h+v*o Inc b Next Math Slice m(),g,,n() 'Box c(),d(),e(),e(),0,,n() pixel c(),d(),n() Math Insert f(),g,,c() Math Insert l(),g,,d() Inc g Next i FRAMEBUFFER COPY f,N 'Print Timer Loop RUN [12] FRAMEBUFFER CREATE F Error : Not enough memory > more pico2 stuff that worked 2040. stan? |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6779 |
Don't create a framebuffer in Mode 3 seems to be the answer. At least, not unless your program takes little RAM, so no big arrays. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
Dim Integer f(41,41),l(41,41),m(41,41) = 41 x 41 x 8 x 3 Bytes = 40,344 Bytes |
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| Bleep Guru Joined: 09/01/2022 Location: United KingdomPosts: 509 |
Here is the version of Bubble that will work on the 2350. It is calculating and updating 2700 points at around 4Hz. I haven't attempted any optimisation for the 2350; yet. bubble2350.bas.zip Edited 2024-09-12 20:42 by Bleep |
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| Sasquatch Guru Joined: 08/05/2020 Location: United StatesPosts: 362 |
Ok, More info on the 720P widescreen modes. I did some reading on the HDMI specification. Seems that full spec signal is 3.3V into 50ohms which would require a drive current of some 66mA. Not really compatible with microcontroller output pins, hence the 220ohm current limiting resistors we are using. Also read somewhere about signal rise times in the order of 100ps. Yikes! So given that we likely have sub spec drive levels and the high speed signal requirements, I removed the Adafruit HDMI breakout board from the solderless breadboard and twisted each pair (+/- for each signal pair) of Dupont leads connecting them directly to the HDMI breakout. The Pico2 end is still on the solderless breadboard connected by Dupont leads.  Happy News! All the TV's and Monitors I have tested have a nice stable sync at 720P and a perfect widescreen picture.  DOH! Seems my setup was at the Bleeding Edge of working and the 720P modes pushed it over the "edges". I don't know why I didn't realize this sooner? I was aware that the solderless breadboard added a lot of capacitance. I guess I was fooled by the setup working so well at 640X480.Anyhow, for those struggling to get their HDMI displays working with the Widescreen 720P modes, try to clean up your wiring setup keeping in mind we are dealing with higher speed signals than we usually encounter. Better grounding might also help in this situation. Please let us know what you find out! My Olimex boards should arrive today, which will eliminate the wire nest I am currently using. -Carl |
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| Sasquatch Guru Joined: 08/05/2020 Location: United StatesPosts: 362 |
I just had another thought! I know, I know, it scares me too! If we used a differential driver IC (with complementary 3.3V outputs) could the HDMI interface be reduced to 4 I/O pins? One I/O pin for each HDMI channel (CLK, D0, D1, D2) and the driver IC would generate the differential signals for each channel. Not sure if the HSTX peripheral could be configured this way. Need to find some data sheets and do some digging when I get some time. -Carl |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 857 |
@Sasquatch This would be cool  I use a lot of the MC3486 receivers but they are 5V. Edited 2024-09-13 13:39 by PhenixRising |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4222 |
Hi Phenix, No chance.... - 3486 are receivers, but even when they would be transmitters, they are far to slow. They have 30ns propagation delay. DVI is running 30MHz clock (that is 33ns). So the driver has almost 1 full clock cycle delay (*). Volhout (*) it is not the delay that is killing, but the difference in delay between channels. With a 30ns per driver delay, delay difference between channels (or different chips) will kill DVI. PicomiteVGA PETSCII ROBOTS |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9105 |
Don't know what part could/would meet the spec but, for example, the MC3486 is at least an order of magnitude too slow. For 720P the clock is running at 186MHz so you need rise times of maximum a couple of nano seconds |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6097 |
Perhaps someone would like to try a HDMI Booster or splitter. Prices vary and as usual the specs are many and varied but they 'should' do the job. Jim Edited 2024-09-13 17:17 by TassyJim VK7JH MMedit MMBasic Help |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6779 |
You might get away with 8 emitter followers if you can find some fast enough devices. That would give a lower impedance output, a better match into 50R. MOSFETs might have too much gate capacitance to work from the Pico outputs so fast BJTs might be better. 200MHz is still within the realms of possibility for VHF transistors. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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