Raspberry Pi 4 Thread - general discussion

[W. H. Heydt]

The full peripheral spec document isn't quite ready yet. 300 pages of proof reading needed....

/shudder A couple of weeks ago I did a proofreading pass over a 400 page manuscript of my wife's WIP. But that was fiction. Easy to read and no verification of actual facts required.

[6by9]

Hi,

I received my Raspberry Pi 4B today. Seems fantastic so far!

One problem I have encountered is getting my DPI display to work. It works great on my 3B+, but it's all black on my 4B. It's one of these: https://www.waveshare.com/wiki/7inch_LCD_for_Pi

I'm basically using the configuration lines from that page:

Code: Select all

dtoverlay=dpi24
enable_dpi_lcd=1
display_default_lcd=1

dpi_group=2
dpi_mode=87
dpi_output_format=0x6f005
hdmi_cvt=1024 600 60 6 0 0 0

It uses the documented backward compatible hdmi_cvt entry. Just an idea, but has this perhaps stopped working on RPi 4? Do I need to craft a dpi_timings entry instead? I tried to construct one from the panel data sheet, but it's pretty tough. ( https://www.waveshare.com/w/upload/1/1a ... LCD_DS.pdf )

Or if that isn't it, any other ideas? Thank you!

hdmi_cvt will apply to the HDMI port (which will be active at the same time. I don't recall if it got duplicated to dpi_cvt or not.

If not, then running "cvt 1024 600 60" gives the standardised timings for that mode.

Code: Select all

$ cvt 1024 600 60
# 1024x600 59.85 Hz (CVT) hsync: 37.35 kHz; pclk: 49.00 MHz
Modeline "1024x600_60.00"   49.00  1024 1072 1168 1312  600 603 613 624 -hsync +vsync

That's not quite in the right format for dpi_timings.
That format is https://github.com/raspberrypi/linux/bl ... des.h#L157 where you can see values are cumulative. For dpi_timings they are independent, so a little bit of subtraction is required.

[PeterO]

The demos in /opt/vc/src/hello_pi/ all (well the ones I've tried) print "This demo application is not available on the Pi4"

Will they be updated ?

PeterO

Maybe. It's whether it's a good use of engineering time. If anyone out there wants to do it and provide a PR, I am most welcoming!

See
https://www.raspberrypi.org/forums/view ... 1#p1486325
PeterO

[tomasf]

If not, then running "cvt 1024 600 60" gives the standardised timings for that mode.

Code: Select all

$ cvt 1024 600 60
# 1024x600 59.85 Hz (CVT) hsync: 37.35 kHz; pclk: 49.00 MHz
Modeline "1024x600_60.00"   49.00  1024 1072 1168 1312  600 603 613 624 -hsync +vsync

That's not quite in the right format for dpi_timings.
That format is https://github.com/raspberrypi/linux/bl ... des.h#L157 where you can see values are cumulative. For dpi_timings they are independent, so a little bit of subtraction is required.

Thanks for that. Very useful.
I constructed a `dpi_timings` from this and got: `dpi_timings=1024 1 48 96 144 600 0 3 10 11 0 0 0 60 0 49000000 3`.
Sadly, it doesn't work. Here's my thinking behind each parameter:

Code: Select all

1024  (horizontal pixels)   self-explanatory
1  (invert hsync)           I suppose this corresponds to "-hsync" in the cvt output. Negative sounds like it would be considered to be inverted?
48  (h front porch)         hsync_start-hdisplay (1072-1024 = 48)
96  (hsync pulse width)     hsync_end-hsync_start (1168-1072 = 96)
144  (h back porch)         htotal-hsync_end (1312-1168 = 144)

600  (vertical pixels)      self-explanatory
0  (invert vsync)           Corresponds to +vsync? See above.
3  (v front porch)          vsync_start-vdisplay (603-600 = 3)
10  (v sync pulse width)    vsync_end-vsync_start (613-603 = 10)
11  (v back porch)          vtotal-vsync_end (624-613 = 11)

0  (v sync offset a)        should be zero according to docs
0  (v sync offset b)        ditto
0  (pixel rep)              ditto
60  (frame rate)            self-explanatory
0  (interlaced)             zero according to docs
49000000  (pixel frequency) 49 MHz from cvt output. Makes sense and is within the range according to that datasheet.
3  (aspect ratio)           15/9 is the closest aspect ratio in the list. Actual aspect ratio is 128/75.

I tried all four combinations of inverted [hv]sync, but to no avail. Screen is still just black.
Is there anything obviously wrong with these values? Thanks!

[6by9]

Thanks for that. Very useful.
I constructed a `dpi_timings` from this and got: `dpi_timings=1024 1 48 96 144 600 0 3 10 11 0 0 0 60 0 49000000 3`.
Sadly, it doesn't work. Here's my thinking behind each parameter:

Code: Select all

1024  (horizontal pixels)   self-explanatory
1  (invert hsync)           I suppose this corresponds to "-hsync" in the cvt output. Negative sounds like it would be considered to be inverted?
48  (h front porch)         hsync_start-hdisplay (1072-1024 = 48)
96  (hsync pulse width)     hsync_end-hsync_start (1168-1072 = 96)
144  (h back porch)         htotal-hsync_end (1312-1168 = 144)

600  (vertical pixels)      self-explanatory
0  (invert vsync)           Corresponds to +vsync? See above.
3  (v front porch)          vsync_start-vdisplay (603-600 = 3)
10  (v sync pulse width)    vsync_end-vsync_start (613-603 = 10)
11  (v back porch)          vtotal-vsync_end (624-613 = 11)

0  (v sync offset a)        should be zero according to docs
0  (v sync offset b)        ditto
0  (pixel rep)              ditto
60  (frame rate)            self-explanatory
0  (interlaced)             zero according to docs
49000000  (pixel frequency) 49 MHz from cvt output. Makes sense and is within the range according to that datasheet.
3  (aspect ratio)           15/9 is the closest aspect ratio in the list. Actual aspect ratio is 128/75.

I tried all four combinations of inverted [hv]sync, but to no avail. Screen is still just black.
Is there anything obviously wrong with these values? Thanks!

I'll try and pull out the full timings that your hdmi_cvt line applies when I'm in the office tomorrow.

[solar3000]

Buster?

busterCrabbe.jpg (107.08 KiB) Viewed 5286 times

[W. H. Heydt]

Buster?

The reference is to the dog in the Toy Story movies. Your picture, however, is Crabbe as Flash Gordon. (And, no, I didn't have to look that up.)

[solar3000]

I'm still waiting for pi 6. I demand the engineers get to work right away.

So, I just got a pi4b 2GB, others were sold out. 4GB sold out. I'm downloading image file and flashing uSD right now....
Glad I live a few miles from Micro Center. Micro Center should pay me for advertising for them.

[solar3000]

Buster?

The reference is to the dog in the Toy Story movies. Your picture, however, is Crabbe as Flash Gordon. (And, no, I didn't have to look that up.)

Oh, I was watching an old video of Caspa the Lion Man starring Buster Crabbe and then.....I see the news about the pi 4 running Buster.

[jahboater]

I see sdram_freq defaults to 3200!

That's a big improvement from 450 ....

[RetroVortex1]

I managed to get Retroarch running on the Pi 4.
Considering the situation so far, it's running very well already.
https://www.youtube.com/watch?v=H75WczEJBGI

[W. H. Heydt]

I'm still waiting for pi 6. I demand the engineers get to work right away.

There are probably folks at RPT already thinking about the Pi6, while the Pi5 is probably already starting to be sketched out.

So, I just got a pi4b 2GB, others were sold out. 4GB sold out. I'm downloading image file and flashing uSD right now....
Glad I live a few miles from Micro Center. Micro Center should pay me for advertising for them.

That's consistent with the initial manufacturing mix and the RPT/RPF expectations of usage patterns, as compared to what the early adopters went for.

[John_Spikowski]

The base RPi 4 B should have started off at 4 GB with a socket to add more.

[rpdom]

I'm still waiting for pi 6. I demand the engineers get to work right away.

There are probably folks at RPT already thinking about the Pi6, while the Pi5 is probably already starting to be sketched out.

jamesh mentioned that they had been discussing the Pi6 a few days ago.

[rpdom]

The base RPi 4 B should have started off at 4 GB with a socket to add more.

Which would have broken the $35 price point. Either that, or other features would have to be left out.

[Heater]

ScriptBasic,

The base RPi 4 B should have started off at 4 GB with a socket to add more.

That made me chuckle. It's not 1980 and a DIP 2K DIP RAM expansion for your Z80 SBC.

Have you ever even seen a socket for a Ball Grid Array RAM chip?

Last time I used sockets for surface mount FLASH chips the socket cost more than the 4GB Pi4.

Where would this socket go on the board?

[Sjurdur]

I’m new here and to the Pi and PC hardware world. Maybe this is an already answered question, but I have a spare pcie nvme ssd lying around and was wondering if a pcie nvme to usb 3.0 enclosure would work with the pi4b ?
This article lists a few enclosures to give you an idea of what I am talking about: https://www.anandtech.com/show/13953/pl ... ule-review

Is this technically possible? Or is the pi limited to only sata drives?

[okenido]

The base RPi 4 B should have started off at 4 GB with a socket to add more.

everyone has different needs, personnally I'd even like a 512MB version since my usage needs very little RAM.

4GB is plenty for a computer with this processing power, 8GB would be quite ridiculous, it's the amount of RAM most desktop x86 computers have, they are an order of magnitude more powerful than a Pi....

[RaTTuS]

This article lists a few enclosures to give you an idea of what I am talking about: https://www.anandtech.com/show/13953/pl ... ule-review

Is this technically possible? Or is the pi limited to only sata drives?

if you plug it into the usb 3 socket you will get usb3 speeds

[Fidelius]

Can we get any more information on the expected computational capabilities and performance difference of the VC6 GPU compared to the VC4?

It's about 4x faster than the VC4 (pixel rate IIRC). So you if you are running full screen 4k, then you get about the same frame rate as the older devices at 1080p.

Factor 4 sounds very good. (Not to confuse with "Factor 5" and their Turrican.)

This Pi4 seems to be an impressive machine. Indeed the biggest jump in the Pi series.

[jamesh]

The base RPi 4 B should have started off at 4 GB with a socket to add more.

Nope.

[EdwinJ85]

When I woke up on announcment day I thought it was another April fools. You've added pretty much every improvement I've wanted for years - well done all, no idea how you pulled it off at the same price point.

I was a little confused about the two mini micro (thanks Peter!) HDMI ports vs one full size one, but I assume there are industrial customers who want this and I'm not the target market for such a feature. Fingers crossed we get the option for a full size port again later down the line.

The main issue I've always had at code clubs and jams and the like is explaining why a Pi can't play higher resolution youtube video well to teachers/parents and the like and trying to get them to look at the other strengths. Now I can just point out it's probably on par with or better than their decade old budget desktops or laptops but with a whole load of extras for less money. I've seen IT suites in schools with worse specced windows machines and there's plenty of chromebooks with less RAM. The ability to properly run electron apps (with some fiddling) like VSCode is going to be a large boon as well.

tl;dr - thank you everybody at Raspberry Pi. I'll do my best to get schools and libraries to spend their tech budgets on these.

[laurent]

Out of curiosity : do this new SoC integrates a RTC (with battery pin exposed) ?
It's not a request, I know it's not useful for almost users and for those who it's useful, there is plenty of third party boards out there. But sometimes it's just available on some SoC.

[PeterO]

I was a little confused about the two mini HDMI ports vs one full size one,

FYI they are micro HDMI not mini HDMI.
PeterO

[jamesh]

Out of curiosity : do this new SoC integrates a RTC (with battery pin exposed) ?
It's not a request, I know it's not useful for almost users and for those who it's useful, there is plenty of third party boards out there. But sometimes it's just available on some SoC.

No.