MarkTF
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Re: PiZero Roadmap

Tue Apr 12, 2016 1:45 pm

mattmiller wrote:I was wondering if someone with some real knowledge (Liz? Eben?) would mind giving us some sort of broad idea of possible Pi Zero wider availability?
Yesterday I sent money to the C.H.I.P guys who promised in return to send me a very inexpensive Linux/ARM computer sometime before June.

On past experience it follows that the Pi Zero will become widely available within the week, will be heavily discounted by the end of the month, and will be given away in breakfast cereal boxes by the time C.H.I.P goes bankrupt in May.

jamesh
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Re: PiZero Roadmap

Tue Apr 12, 2016 1:47 pm

MarkTF wrote:
mattmiller wrote:I was wondering if someone with some real knowledge (Liz? Eben?) would mind giving us some sort of broad idea of possible Pi Zero wider availability?
Yesterday I sent money to the C.H.I.P guys who promised in return to send me a very inexpensive Linux/ARM computer sometime before June.

On past experience it follows that the Pi Zero will become widely available within the week, will be heavily discounted by the end of the month, and will be given away in breakfast cereal boxes by the time C.H.I.P goes bankrupt in May.
Yup, think that about covers it.
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Re: PiZero Roadmap

Tue Apr 12, 2016 1:54 pm

Massi wrote:will it be a "simple" software new feature (lan boot? usb boot?) or something hardware? :lol:
someone said "revision" ( viewtopic.php?f=63&t=144190&view=unread#p951367 ) so definitely it's something hardware :)

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Re: PiZero Roadmap

Tue Apr 12, 2016 2:25 pm

hippy wrote:It could be the provision of USB/PXE booting.
Since that requires internal support on the SoC, I think that feature can be reasonably ruled out.

Massi
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Re: PiZero Roadmap

Tue Apr 12, 2016 2:47 pm

W. H. Heydt wrote:
hippy wrote:It could be the provision of USB/PXE booting.
Since that requires internal support on the SoC, I think that feature can be reasonably ruled out.
stupid me, it's a Pi3 feature that still has to arrive, not a Zero one..

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Re: PiZero Roadmap

Tue Apr 12, 2016 3:02 pm

W. H. Heydt wrote:
hippy wrote:It could be the provision of USB/PXE booting.
Since that requires internal support on the SoC, I think that feature can be reasonably ruled out.
Does it require SoC support though; is there something more on the BCM2837 than is available on the BCM2835 or BCM2836 ?

I honestly don't know. I thought the VideoCore and peripheral parts were the same ( apart from peripheral base address ) and the GPU is the only thing running when the SoC comes out of reset and it's that which would handle USB/PXE booting.

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Re: PiZero Roadmap

Tue Apr 12, 2016 3:12 pm

hippy wrote:Does it require SoC support though; is there something more on the BCM2837 than is available on the BCM2835 or BCM2836 ?

I honestly don't know. I thought the VideoCore and peripheral parts were the same ( apart from peripheral base address ) and the GPU is the only thing running when the SoC comes out of reset and it's that which would handle USB/PXE booting.
It's a bootrom change with BCM2837. ROM being genuinely programmed into the silicon with no way of changing it.
The contents of a ROM can be changed fairly easily before fabrication without changing any of the real processing side of things. (Getting it wrong is a very expensive mistake though!)
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Re: PiZero Roadmap

Tue Apr 12, 2016 6:34 pm

So the circuit board is being redesigned to allow automated testing by Sony. So we're talking about a simple cost neutral change to the main circuit board only.

My guess would be an audio breakout similar to the current video breakout. That would be cost neutral seeing as the main board is already being redesigned. Not sure if that would require a software update though.

I would love it to be the DSI camera connector but that requires major circuitry and an expensive connector (relatively)
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Re: PiZero Roadmap

Tue Apr 12, 2016 7:00 pm

6by9 wrote:
hippy wrote:Does it require SoC support though; is there something more on the BCM2837 than is available on the BCM2835 or BCM2836 ?

I honestly don't know. I thought the VideoCore and peripheral parts were the same ( apart from peripheral base address ) and the GPU is the only thing running when the SoC comes out of reset and it's that which would handle USB/PXE booting.
It's a bootrom change with BCM2837. ROM being genuinely programmed into the silicon with no way of changing it.
The contents of a ROM can be changed fairly easily before fabrication without changing any of the real processing side of things. (Getting it wrong is a very expensive mistake though!)
A bit of background.

Gordon produced an updated bootrom for the chip in August last year, and after testing by David Lewsey at Broadcom this was incorporated into the "A1" spin of the chip in time for production. The increment from "A0" to "A1" signifies a metal-only spin of the device (either to fix bugs or in this case to update a mask-programmable ROM); an increment to "B0" would generally signify an all-layers change (a full tapeout). The three chips used in Raspberry Pi products have been BCM2835C1, BCM2836A0 (always satisfying to go "A0 to production") and BCM2837A1.

In related news, I saw a nearly complete USB mass storage boot on Raspberry Pi 3 today.

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Re: PiZero Roadmap

Tue Apr 12, 2016 7:28 pm

eupton wrote:A bit of background.

Gordon produced an updated bootrom for the chip in August last year, and after testing by David Lewsey at Broadcom this was incorporated into the "A1" spin of the chip in time for production. The increment from "A0" to "A1" signifies a metal-only spin of the device (either to fix bugs or in this case to update a mask-programmable ROM); an increment to "B0" would generally signify an all-layers change (a full tapeout). The three chips used in Raspberry Pi products have been BCM2835C1, BCM2836A0 (always satisfying to go "A0 to production") and BCM2837A1.
(Hmm, how about a metal-only spin to BCM2835 and BCM2836 to have the new bootrom code in there..... :ugeek: rumour mill into overdrive! One step at a time, and even a metal-only spin isn't cheap)
eupton wrote:In related news, I saw a nearly complete USB mass storage boot on Raspberry Pi 3 today.
You never can stop Gordon tinkering, but I'm surprised he didn't have it all running within 5 minutes of the chip being mounted to a board :D

(NB I have no knowledge whatsoever as to what is planned, and I am not employed by Pi Towers, so this is pure rumour and speculation! Do not treat it as official information on what will happen)
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Re: PiZero Roadmap

Tue Apr 12, 2016 7:57 pm

Massi wrote:
W. H. Heydt wrote:
hippy wrote:It could be the provision of USB/PXE booting.
Since that requires internal support on the SoC, I think that feature can be reasonably ruled out.
stupid me, it's a Pi3 feature that still has to arrive, not a Zero one..
Pure USB booting would require adding a BIOS to the board, a fairly major change I would think. Feel free to correct me as I am not as knowledgeable as many on here.

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Re: PiZero Roadmap

Tue Apr 12, 2016 8:33 pm

Koeshi wrote:Pure USB booting would require adding a BIOS to the board, a fairly major change I would think. Feel free to correct me as I am not as knowledgeable as many on here.
On Pi, the equivalent to the BIOS is the bootrom. That has been updated on Pi3 and supports talking to USB mass storage, and ethernet.
The bootrom has always existed, but until Pi3 it only supported booting form SD card, eMMC flash (as used on the Compute Module), or a few methods that aren't applicable to Pi.

There is a second stage loader that still needs some work before USB or ethernet boot is fully functional - Pi Towers are on it.
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Re: PiZero Roadmap

Tue Apr 12, 2016 8:36 pm

The RPi 1st stage bootloader is in the VideoCore IV VPU

http://wiki.beyondlogic.org/index.php?t ... ot_Process
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Re: PiZero Roadmap

Tue Apr 12, 2016 8:55 pm

6by9 wrote:
Koeshi wrote:Pure USB booting would require adding a BIOS to the board, a fairly major change I would think. Feel free to correct me as I am not as knowledgeable as many on here.
On Pi, the equivalent to the BIOS is the bootrom. That has been updated on Pi3 and supports talking to USB mass storage, and ethernet.
The bootrom has always existed, but until Pi3 it only supported booting form SD card, eMMC flash (as used on the Compute Module), or a few methods that aren't applicable to Pi.

There is a second stage loader that still needs some work before USB or ethernet boot is fully functional - Pi Towers are on it.
Forgive me if I am mistaken, as said I am not as knowledgeable as many.

I thought the only way to boot from USB was to have an SD card in place that functioned as the BIOS. Wouldn't adding a BIOS (or bootROM) capable of booting straight from the USB with no SDcard input require a significant change, as in something that couldn't be done to pre-existing Pis but instead at the manufacturing stage?

@fruitoftheloom, I appreciate the link but sadly it doesn't mean much to me :(

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Re: PiZero Roadmap

Tue Apr 12, 2016 9:08 pm

Koeshi wrote:Forgive me if I am mistaken, as said I am not as knowledgeable as many.

I thought the only way to boot from USB was to have an SD card in place that functioned as the BIOS. Wouldn't adding a BIOS (or bootROM) capable of booting straight from the USB with no SDcard input require a significant change, as in something that couldn't be done to pre-existing Pis but instead at the manufacturing stage?
viewtopic.php?f=63&t=144165&start=25#p951609
That change to the bootrom (BIOS) has been done on the BCM2837 used in the Pi3.
The 2nd stage loader is currently bootcode.bin, which is found in /boot of your SD card. That will be what will be collected from USB storage or network, and then proceeds to complete the rest of the boot. That is the work that needs to be completed.

Updating Pi1 or Pi2 devices would require a new chip, so is not an upgrade option for existing Pi's.
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Re: PiZero Roadmap

Tue Apr 12, 2016 9:12 pm

Koeshi wrote:
6by9 wrote:
Koeshi wrote:Pure USB booting would require adding a BIOS to the board, a fairly major change I would think. Feel free to correct me as I am not as knowledgeable as many on here.
On Pi, the equivalent to the BIOS is the bootrom. That has been updated on Pi3 and supports talking to USB mass storage, and ethernet.
The bootrom has always existed, but until Pi3 it only supported booting form SD card, eMMC flash (as used on the Compute Module), or a few methods that aren't applicable to Pi.

There is a second stage loader that still needs some work before USB or ethernet boot is fully functional - Pi Towers are on it.
Forgive me if I am mistaken, as said I am not as knowledgeable as many.

I thought the only way to boot from USB was to have an SD card in place that functioned as the BIOS. Wouldn't adding a BIOS (or bootROM) capable of booting straight from the USB with no SDcard input require a significant change, as in something that couldn't be done to pre-existing Pis but instead at the manufacturing stage?

@fruitoftheloom, I appreciate the link but sadly it doesn't mean much to me :(
You are correct...as far as you've gone. The key thing missing is that the change *was* made to the 2837 chip by adding code to the boot ROM that is part of the chip. The next step is bootloader code on the targetted external device.

The logic is probably something like:
1. Look for an SD or eMMC.
--if found, load the second stage boot from it.
2. If not found, look for a USB device with a second state boot file.
--if found, load the second stage boot code from that device.

What needs to happen (and is--apparently--pretty close to working) is for the second stage boot code that will be able to determine what device it cam from (SD, eMMC, USB device) and get the third and subsequent code stages from the same device.

(I'll let those with systems programming experience tell me if I've gotten that wrong beyond just oversimplification.)

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Re: PiZero Roadmap

Tue Apr 12, 2016 9:28 pm

So is it possible to make the change to existing Pi3 chips so that they will be able to boot directly from USB without SD input?

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Re: PiZero Roadmap

Tue Apr 12, 2016 9:32 pm

Koeshi wrote:So is it possible to make the change to existing Pi3 chips so that they will be able to boot directly from USB without SD input?
That change has already been made on the chip itself, it's the bootloader on the USB or Ethernet that needs work.
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Re: PiZero Roadmap

Tue Apr 12, 2016 9:56 pm

Massi wrote:will it be a "simple" software new feature (lan boot? usb boot?) or something hardware? :lol:
Is USB boot at all possible?
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Re: PiZero Roadmap

Tue Apr 12, 2016 9:57 pm

Cancelor wrote:
Massi wrote:will it be a "simple" software new feature (lan boot? usb boot?) or something hardware? :lol:
Is USB boot at all possible?
Yes. As said before, it just needs the correct second stage bootloader.
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Re: PiZero Roadmap

Tue Apr 12, 2016 10:06 pm

Cancelor wrote:
Massi wrote:will it be a "simple" software new feature (lan boot? usb boot?) or something hardware? :lol:
Is USB boot at all possible?
viewtopic.php?f=63&t=144165&start=25#p951609
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Re: PiZero Roadmap

Tue Apr 12, 2016 10:09 pm

kusti8 wrote:
Koeshi wrote:So is it possible to make the change to existing Pi3 chips so that they will be able to boot directly from USB without SD input?
That change has already been made on the chip itself, it's the bootloader on the USB or Ethernet that needs work.
Ah I see where I was misunderstanding, thank you.

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Re: PiZero Roadmap

Tue Apr 12, 2016 10:11 pm

kusti8 wrote:
Cancelor wrote:
Massi wrote:will it be a "simple" software new feature (lan boot? usb boot?) or something hardware? :lol:
Is USB boot at all possible?
Yes. As said before, it just needs the correct second stage bootloader.
That is true for the Pi 3. On the Pi Zero, the bootROM in the BCM2835 needs updating, which is a revision to the chip. Possible, but we are all guessing about whether that is the one. It would have the side effect of bringing the booting of A+ and B+ into line with the Pi 3. The Pi 2 would need an equivalent change to its bootROM -- still possible, but less likely. (I guess that having made the change for the 2837 it is comparatively risk-free to port it to the others. And note Eben mentioned the chip revision numbers for all three -- or was that smoke and mirrors?)
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Re: PiZero Roadmap

Tue Apr 12, 2016 10:13 pm

Let me get out my tarot cards and see.............
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Re: PiZero Roadmap

Tue Apr 12, 2016 10:20 pm

davidcoton wrote: That is true for the Pi 3. On the Pi Zero, the bootROM in the BCM2835 needs updating, which is a revision to the chip. Possible, but we are all guessing about whether that is the one. It would have the side effect of bringing the booting of A+ and B+ into line with the Pi 3. The Pi 2 would need an equivalent change to its bootROM -- still possible, but less likely. (I guess that having made the change for the 2837 it is comparatively risk-free to port it to the others. And note Eben mentioned the chip revision numbers for all three -- or was that smoke and mirrors?)
The BOOTROM is in the VC4 VPU, which is common to all RPi SoC's, therefore it "could" be implemented in all future SoC Manufacturing.....

...but it may already be implemented in BCM2835 & BCM2836 SoC's manufactured after August 2015, as well as the BCM2837 ??


Unfortunately it can not be retrospectively implemented, so any new Firmware would need to check for the BOOTROM capabilities !!


Be great if USB BOOT was actually already in the BCM2835 SoC of the ZERO :D
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