W. H. Heydt
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Then there's the *other* feature...

Mon Oct 19, 2020 11:46 pm

Lots of talk about the CM4. Some about the new dev (IO) carrier board...especially the price.

What I haven't seen anyone mention is the other interesting feature of the dev carrier...it has an RTC and battery holder. Is this the shape of things to come?

cleverca22
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Re: Then there's the *other* feature...

Mon Oct 19, 2020 11:54 pm

one annoying thing i noticed with the rtc, is wired to the global_en signal

so if the rtc alarm fires while the cm4 is running, it causes a hard reset, potentially corrupting data

but using gpio3 and WAKE_ON_GPIO would have eaten a gpio that the user may be using, so i can see why they made the choice

W. H. Heydt
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 12:39 am

cleverca22 wrote:
Mon Oct 19, 2020 11:54 pm
one annoying thing i noticed with the rtc, is wired to the global_en signal

so if the rtc alarm fires while the cm4 is running, it causes a hard reset, potentially corrupting data

but using gpio3 and WAKE_ON_GPIO would have eaten a gpio that the user may be using, so i can see why they made the choice
That does create some interesting possibilities... One is, shut down RTC alarms when the board is running. Another is a "wake at this pre-set time" function.

cjan
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 1:08 am

I/O board cheap but looks large and ugly, wait 3rd party board.

cleverca22
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 1:13 am

from a glance at the pinouts, all of the high speed (dsi, csi, hdmi, ethernet, pci, usb) is on one connector almost exclusively

the 2nd connector is lowspeed and power

it looks plausible to run the entire CM4 from just the low-speed side, if you dont want any of the high-speed things, and with the built-in wifi, it would still have some connectivity, but the lack of usb could harm the user-interaction part of IO

and with the onboard regulators, you could even run it with just a 5v source, and zero external components, so its basically a pi0 at that point, just add your own IO headers for bits you want

W. H. Heydt
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 5:12 am

cleverca22 wrote:
Tue Oct 20, 2020 1:13 am
from a glance at the pinouts, all of the high speed (dsi, csi, hdmi, ethernet, pci, usb) is on one connector almost exclusively

the 2nd connector is lowspeed and power

it looks plausible to run the entire CM4 from just the low-speed side, if you dont want any of the high-speed things, and with the built-in wifi, it would still have some connectivity, but the lack of usb could harm the user-interaction part of IO

and with the onboard regulators, you could even run it with just a 5v source, and zero external components, so its basically a pi0 at that point, just add your own IO headers for bits you want
On the other hand, the cheapest CM4 that could run anything and communicate with the outside world, would be $35, since you'll need eMMC and WiFi. Nearest comparison is to the $10 Pi0W.

aBUGSworstnightmare
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 5:42 am

cleverca22 wrote:
Tue Oct 20, 2020 1:13 am
from a glance at the pinouts, all of the high speed (dsi, csi, hdmi, ethernet, pci, usb) is on one connector almost exclusively

the 2nd connector is lowspeed and power

it looks plausible to run the entire CM4 from just the low-speed side, if you dont want any of the high-speed things, and with the built-in wifi, it would still have some connectivity, but the lack of usb could harm the user-interaction part of IO

and with the onboard regulators, you could even run it with just a 5v source, and zero external components, so its basically a pi0 at that point, just add your own IO headers for bits you want
Why not add a USB2.0 speed hub similar to what's been done on the CM4IO or simple route the OTG port only? Still 'low speed' ..
Last edited by aBUGSworstnightmare on Tue Oct 20, 2020 7:59 am, edited 2 times in total.

jdb
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 7:25 am

cjan wrote:
Tue Oct 20, 2020 1:08 am
I/O board cheap but looks large and ugly, wait 3rd party board.
Thanks for the detailed feedback, I'll be sure to pass it along
Rockets are loud.
https://astro-pi.org

fruitoftheloom
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 7:32 am

.
What is the purpose of the Fan and Power Connectors top right of the I/O Board ??
The information is out there....you just have to let it in.

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Re: Then there's the *other* feature...

Tue Oct 20, 2020 7:53 am

Errr, receiving power and driving a fan?

I think the PCIe slot can take a bit more power than the regular 12v supply can manage.

fruitoftheloom
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 8:06 am

PhilE wrote:
Tue Oct 20, 2020 7:53 am
Errr, receiving power and driving a fan?

I think the PCIe slot can take a bit more power than the regular 12v supply can manage.

Yes quite, but in layman's terms what voltage, amps, watts. Surely there must have been a reason for the inclusion, but not mentioned in the Official Video.
The information is out there....you just have to let it in.

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Re: Then there's the *other* feature...

Tue Oct 20, 2020 8:18 am

--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

Technocolour
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 8:19 am

The inclusion is for people who wants a fan and /or to drive some external thingamabob in their designs and wants an easy template to start with?

PhilE
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 8:45 am

From the datasheet:
This connector supports standard +12V FANs with PWM drive and tacho output. An EMC2301 controls the fan via I2C.
Mating connector part number Molex 47054-1000 or similar. The +12V power for the fan comes from the +12V input and
isn’t regulated.
The main PSU input (J19) is a 2.1mm DC tip positive +12V input. On board there is a +12V to +5V DC-DC converter to
power the CM4. There is also an on-board +12V to +3.3V DC-DC converter PSU which is only used for the PCIe slot. The
+12V input feeds the +12V PCIe slot, the external PSU connect and the FAN connector directly. If these aren’t being used
then a wider input supply is possible ( +7.5V to +26V).
With a +12V supply via the DC barrel jack the external PSU connector ( J20, +5V, +12V ) is ideal to connect to PCIe cards
that require external PSU. You should ensure that the PSUs aren’t over loaded. J20 Matting connector is known as "Berg"
Part number AMP / TE Connectivity 171822-4 or similar.
The exact current required from the +12V PSU is dependent on the application and what is connected to the Raspberry Pi
Compute Module 4 IO Board. It is recommended to budget 9W for the CM4.

fanoush
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 9:08 am

jdb wrote:
Tue Oct 20, 2020 7:25 am
cjan wrote:
Tue Oct 20, 2020 1:08 am
I/O board cheap but looks large and ugly, wait 3rd party board.
Thanks for the detailed feedback, I'll be sure to pass it along
Sorry for not detailed feedback but I like it a lot - the extra 2x USB 2.0 on pinheader, the rtc, the 12V (better than just 5) and the pci express of course. This I/O board is great for me and also I very much like the raspberry pi styled price ($35).

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bensimmo
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 9:24 am

fanoush wrote:
Tue Oct 20, 2020 9:08 am
jdb wrote:
Tue Oct 20, 2020 7:25 am
cjan wrote:
Tue Oct 20, 2020 1:08 am
I/O board cheap but looks large and ugly, wait 3rd party board.
Thanks for the detailed feedback, I'll be sure to pass it along
Sorry for not detailed feedback but I like it a lot - the extra 2x USB 2.0 on pinheader, the rtc, the 12V (better than just 5) and the pci express of course. This I/O board is great for me and also I very much like the raspberry pi styled price ($35).
The 12V input sets it up to be used with the up and coming ATX12VO PSU's that should be replacing current PC PSU's eventually. i.e. they'll all take a 12V input and the motherboards now have to do the conversion. These PSU doesn't create the 5V, 3V3 lines any more

jamesh
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 10:20 am

cjan wrote:
Tue Oct 20, 2020 1:08 am
I/O board cheap but looks large and ugly, wait 3rd party board.
I think you are misunderstanding what the IO board is actually for. Its a DEV board, for people to test out the CM before making their own boards.

It therefor has no need whatsoever to "look nice" or "be small"
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 10:29 am

jamesh wrote:
Tue Oct 20, 2020 10:20 am
cjan wrote:
Tue Oct 20, 2020 1:08 am
I/O board cheap but looks large and ugly, wait 3rd party board.
I think you are misunderstanding what the IO board is actually for. Its a DEV board, for people to test out the CM before making their own boards.

It therefor has no need whatsoever to "look nice" or "be small"
ok, sorry & thanks.

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Re: Then there's the *other* feature...

Tue Oct 20, 2020 11:01 am

jamesh wrote:
Tue Oct 20, 2020 10:20 am
I think you are misunderstanding what the IO board is actually for. Its a DEV board, for people to test out the CM before making their own boards.
Eben did say -
In addition to serving as a development platform and reference design, we expect the IO board to be a finished product in its own right: if you require a Raspberry Pi that supports a wider range of input voltages, has all its major connectors in a single plane, or allows you to attach your own PCI Express devices, then Compute Module 4 with the IO Board does what you need.
And I believe he's right.

IMO it's not large nor ugly but exactly what I've wanted from a Pi board since they first arrived. So no complaints from me.

The big win for me is "The Raspberry Pi Compute Module 4 Antenna Kit is certified for use with Raspberry Pi Compute Module 4".

Looks like I might be able to finally build the 'Pi PC' I've wanted without having to bodge cabling and cases to have it how I want. And for not a lot more than it would have cost me.

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Gavinmc42
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 11:07 am

Cannot find the analog audio.
Am I missing something?
I use DVI monitors and analog powered speakers.
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jamesh
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 11:09 am

Gavinmc42 wrote:
Tue Oct 20, 2020 11:07 am
Cannot find the analog audio.
Am I missing something?
I use DVI monitors and analog powered speakers.
Don't believe analogue audio is supported i.e. no socket on the IO board.
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fanoush
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 11:40 am

hippy wrote:
Tue Oct 20, 2020 11:01 am
Eben did say
Can you link the talk? This is actually second reference to such thing without any link (first was somewhere by W. H. Heydt, cannot find it now). Thanks.

hippy
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 11:52 am

fanoush wrote:
Tue Oct 20, 2020 11:40 am
hippy wrote:
Tue Oct 20, 2020 11:01 am
Eben did say
Can you link the talk? This is actually second reference to such thing without any link (first was somewhere by W. H. Heydt, cannot find it now). Thanks.
Sorry, copied the text, back-buttoned to this thread, and forgot to bring the link with me. That was from the Pi Blog -

https://www.raspberrypi.org/blog/raspbe ... -module-4/

fanoush
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 11:55 am

Oh, got it now, near the end "I sat down with Dominic last week to discuss Compute Module 4 in greater detail, and you can find the video of our conversation here. Dominic will also be sharing more technical detail in the blog tomorrow."
https://www.youtube.com/watch?v=yiHgmNB ... e=youtu.be

cleverca22
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Re: Then there's the *other* feature...

Tue Oct 20, 2020 1:49 pm

jamesh wrote:
Tue Oct 20, 2020 11:09 am
Gavinmc42 wrote:
Tue Oct 20, 2020 11:07 am
Cannot find the analog audio.
Am I missing something?
I use DVI monitors and analog powered speakers.
Don't believe analogue audio is supported i.e. no socket on the IO board.
does it at least expose gpio 40/41 somewhere, so the user could add their own low-pass filter and re-enable the PWM audio?

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