Schematics of Raspberry Pi Zero

[corvand]

Are these available ?

[jamesh]

No. GPIO pinout is same as B2.

[hippy]

Is it possible to have clarification on whether a power supply fuse is fitted or not, what the maximum current which can be drawn through the USB socket is ?

Has the over-voltage clamp also been removed ?

How much current can be drawn from the GPIO power pins ?

A list of what electrical changes have been made would be useful even if full circuit diagrams are not provided.

[DougieLawson]

More important is whether it's at risk from PeterO's Xenon Death Flash.

[Laurens-wuyts]

More important is whether it's at risk from PeterO's Xenon Death Flash.

Trail and (hopefully not) error.

Laurens

[mahjongg]

These are my own observations, so its not from an official RPF source:

There is no polyfuse, and no over voltage protection device, and no USB controller (meaning you can backfeed power).
This means that feeding the PI over the 5V GPIO pins is now EXACTLY the same as feeding through the microUSB, there is no additional security in feeding through the microUSB port, except for that you cannot (should not be able to) make wiring mistakes when using microUSB, as said the PI can be powered through either microUSB ports, its makes no difference which one.

There will be no Xenon Death Flash problem, as the Zero uses a different drop down converter (a 2306KE). There is however a flip chip device (U8) which may react to xenon flashes, but probably not by causing a reset, it seems to have something to do with HDMI signal conditioning.

My guess is that a HDMI to VGA adapter can be powered from the HDMI port, there is a large schottky diode that makes it possible to draw much more than 50mA from the HDMI port.

That is it for now.

There is just one LED (shining sideways) the ACT LED, which has no driver FET, so behaves exactly like a PI B.
It will probably initially glow very faint, and only turn on after first having read from the SD-card.
That means there is NO power LED.

I don't believe the SD card has a push to enter push to release mechanism, (but I might be wrong), which means there is no mechanism to damage, no more "the card wont stay in" problems.

I count just 22 test points on the back, while I see higher "PP" numbers, like PP39, this indicates the PP numbers are the same as a previous PI, maybe the same as the B+. Have to look into that but it looks promising, I think I can draw up a list with the use of the testpoints.

J5 (on the back) is the optional connector for JTAG testing, its not for users, same as on the B+.

there is a mystery U13 location, no idea yet what its for, seems to be a SOT23-6 device.
There are also several other unpopulated resistors (or maybe capacitors).

[gregeric]

there is a mystery U13 location, no idea yet what its for, seems to be a SOT23-6 device.
There are also several other unpopulated resistors (or maybe capacitors).

I suspect it's for a USB current-limiting chip. In lieu of it, there's a zero Ohm resistor directly linking PWR IN to the OTG port

[mahjongg]

you could be right, I suspected the zero ohm resistor was a lower cost replacement for the polyfuse, but you might be right.

[Squonk]

I count just 22 test points on the back, while I see higher "PP" numbers, like PP39, this indicates the PP numbers are the same as a previous PI, maybe the same as the B+. Have to look into that but it looks promising, I think I can draw up a list with the use of the testpoints.

Yes, most of test points match the B+, especially PP14-PP19 for SD card, and PP1/3/4/5/6/9 for power supplies/GND.

Maybe PP39-40 are the same SCL0/SDA0 as B+, however, the remaining ones are more questionable: PP20/22/23//35/36/37/38/39/40, especially PP22-23 and PP35-36 that are related to Ethernet on B+, where PP35 here is clearly a GND. PP37-38 on B+ are CAM-GPIO0/1.

So, no CSI

[dsop]

Hi all! I'm in the US and got my zero yesterday, super stoked! A coworker and I were looking over it and the schematics. I plugged the power cord into the OTG port instead of the power port, and now I don't see the 'act' light. Any chance I burned it already?

[gregeric]

The ACT LED does not come on unless you have a uSD card in place. Put a bootable card in the slot & try again. And no, I don't think you can fry it doing what you did.

[rpdom]

You can't kill the Zero by plugging the power into the data USB socket. It will work fine like that. You can't use the power socket for data though.

[gregeric]

I count just 22 test points on the back, while I see higher "PP" numbers, like PP39, this indicates the PP numbers are the same as a previous PI, maybe the same as the B+. Have to look into that but it looks promising, I think I can draw up a list with the use of the testpoints.

Just had a quick go at buzzing these test points out, looking for free GPIO's. Firstly, this is how they look with nothing probed:

Code: Select all

pi@pi-zero ~ $ sudo raspi-gpio get
BANK0 (GPIO 0 to 27):
  GPIO 00: level=1 fsel=0 alt=  func=INPUT
  GPIO 01: level=1 fsel=0 alt=  func=INPUT
  GPIO 02: level=1 fsel=4 alt=0 func=SDA1
  GPIO 03: level=1 fsel=4 alt=0 func=SCL1
  GPIO 04: level=0 fsel=1 alt=  func=OUTPUT
  GPIO 05: level=0 fsel=0 alt=  func=INPUT
  GPIO 06: level=0 fsel=0 alt=  func=INPUT
  GPIO 07: level=1 fsel=4 alt=0 func=SPI0_CE1_N
  GPIO 08: level=1 fsel=4 alt=0 func=SPI0_CE0_N
  GPIO 09: level=0 fsel=4 alt=0 func=SPI0_MISO
  GPIO 10: level=0 fsel=4 alt=0 func=SPI0_MOSI
  GPIO 11: level=0 fsel=4 alt=0 func=SPI0_SCLK
  GPIO 12: level=0 fsel=0 alt=  func=INPUT
  GPIO 13: level=0 fsel=0 alt=  func=INPUT
  GPIO 14: level=1 fsel=4 alt=0 func=TXD0
  GPIO 15: level=0 fsel=4 alt=0 func=RXD0
  GPIO 16: level=0 fsel=0 alt=  func=INPUT
  GPIO 17: level=0 fsel=0 alt=  func=INPUT
  GPIO 18: level=0 fsel=0 alt=  func=INPUT
  GPIO 19: level=0 fsel=0 alt=  func=INPUT
  GPIO 20: level=0 fsel=0 alt=  func=INPUT
  GPIO 21: level=0 fsel=0 alt=  func=INPUT
  GPIO 22: level=0 fsel=0 alt=  func=INPUT
  GPIO 23: level=0 fsel=0 alt=  func=INPUT
  GPIO 24: level=0 fsel=0 alt=  func=INPUT
  GPIO 25: level=0 fsel=0 alt=  func=INPUT
  GPIO 26: level=0 fsel=0 alt=  func=INPUT
  GPIO 27: level=0 fsel=0 alt=  func=INPUT
BANK1 (GPIO 28 to 45):
  GPIO 28: level=1 fsel=4 alt=0 func=SDA0
  GPIO 29: level=1 fsel=4 alt=0 func=SCL0
  GPIO 30: level=0 fsel=0 alt=  func=INPUT
  GPIO 31: level=0 fsel=0 alt=  func=INPUT
  GPIO 32: level=0 fsel=0 alt=  func=INPUT
  GPIO 33: level=0 fsel=0 alt=  func=INPUT
  GPIO 34: level=1 fsel=0 alt=  func=INPUT
  GPIO 35: level=1 fsel=0 alt=  func=INPUT
  GPIO 36: level=1 fsel=0 alt=  func=INPUT
  GPIO 37: level=0 fsel=0 alt=  func=INPUT
  GPIO 38: level=0 fsel=0 alt=  func=INPUT
  GPIO 39: level=0 fsel=0 alt=  func=INPUT
  GPIO 40: level=0 fsel=0 alt=  func=INPUT
  GPIO 41: level=0 fsel=0 alt=  func=INPUT
  GPIO 42: level=0 fsel=0 alt=  func=INPUT
  GPIO 43: level=0 fsel=0 alt=  func=INPUT
  GPIO 44: level=0 fsel=0 alt=  func=INPUT
  GPIO 45: level=0 fsel=0 alt=  func=INPUT
BANK2 (GPIO 46 to 53):
  GPIO 46: level=0 fsel=0 alt=  func=INPUT
  GPIO 47: level=1 fsel=1 alt=  func=OUTPUT
  GPIO 48: level=0 fsel=7 alt=3 func=SD1_CLK
  GPIO 49: level=1 fsel=7 alt=3 func=SD1_CMD
  GPIO 50: level=1 fsel=7 alt=3 func=SD1_DAT0
  GPIO 51: level=1 fsel=7 alt=3 func=SD1_DAT1
  GPIO 52: level=1 fsel=7 alt=3 func=SD1_DAT2
  GPIO 53: level=1 fsel=7 alt=3 func=SD1_DAT3
pi@pi-zero ~ $ 

Guess the ACT LED is at 47, dunno what 34-36 may be used for (run, otg sense?).

Pulling up to 3V3 via 10k and re-running raspi-gpio get, I wasn't able to see any changes, so I think no GPIOs on those pads

[gregeric]

There are a couple of GPIO's available topside on the unpopulated U13, 44 & 45.

Looks like they were for the ENABLE and FAULT signals on that USB current limit chip. The pinout matches a 2553 device.

GPIO44 is the left hand pad nearest the Raspberry logo, 45 the right hand.

PWM1 is available on 45 (useful for sound out).

Code: Select all

GPIO, DEFAULT PULL, ALT0, ALT1, ALT2, ALT3, ALT4, ALT5
44, NONE, GPCLK1, SDA0, SDA1, TE0, SPI2_CE1_N, -
45, NONE, PWM1, SCL0, SCL1, TE1, SPI2_CE2_N, -

[gregeric]

Trying to sniff out another GPIO, I just spent half an hour wondering why I couldn't see one of the 54 GPIOs pulled low on plugging in an OTG cable. Doh, I guess it must be connected to the Synopsys USB PHY peripheral, not a GPIO.

[hippy]

Trying to sniff out another GPIO, I just spent half an hour wondering why I couldn't see one of the 54 GPIOs pulled low on plugging in an OTG cable. Doh, I guess it must be connected to the Synopsys USB PHY peripheral, not a GPIO.

Look at the earlier schematics for the Pi and you will see a separate "USB.OTGID" (K16) pin on the BCM2835, tied to 0V. It is probably that which you are looking for.

[gregeric]

Thanks hippy, should've thought to look there for confirmation.

GPIO46, like on other Pis is used as HDMI-HDP (hotplug detect). If you are running headless that's an extra GPIO input to be had, and maybe a 5V tolerant one at that if taken from HDMI pin 19.

[pixelk]

My Hi-res Photo of the pads if needed (18,2Mo)

http://stuff.knackes.com/dld/201601/Pi0 ... 14042F.png

[gregeric]

Two more GPIOs buzzed out top-side at unpopulated 0402 locations adjacent to the 40-pin header:

GPIO28 immediately to the right of the "GPIO" legend.
GPIO29 lying between the SOC & the header.

Alt funcs:

Code: Select all

GPIO, DEFAULT PULL, ALT0, ALT1, ALT2, ALT3, ALT4, ALT5
28, NONE, SDA0, SA5, PCM_CLK, FL0, -, -
29, NONE, SCL0, SA4, PCM_FS, FL1, -, -

The other end of whatever 0402 component would be mounted there is ground, so not pull-ups for SDA0/SCL0. Any ideas what FL0, FL1 are?

[hippy]

Two more GPIOs buzzed out top-side at unpopulated 0402 locations adjacent to the 40-pin header:

A thought; as well as unpopulated locations, there may also be populated locations which could be used as GPIO if the configurations they achieve were instead implemented solely by software configuration.

I don't know what FL0/FL1 are but they also seem to be ALT-0 functions of GPIO16/GPIO17.

[KevinA]

Hey PI people, I have a suggestion, why not publish the schematics for the Zero so customers can stop poking at the board? The MAN HOURS wasted could be put to use doing something creative....

[occupied]

the PI can be powered through either microUSB ports, its makes no difference which one.

You can't kill the Zero by plugging the power into the data USB socket. It will work fine like that.

A foolish question from the uneducated - what will happen if you connect a power source to both ports at the same time?

[mfa298]

Hey PI people, I have a suggestion, why not publish the schematics for the Zero so customers can stop poking at the board? The MAN HOURS wasted could be put to use doing something creative....

I think the only Schematic that's ever been published was for the Pi1 boards, and those led to various "compatible" clones that weren't really compatible and detracted from the Foundations aims.

[Laurens-wuyts]

A foolish question from the uneducated - what will happen if you connect a power source to both ports at the same time?

Nothing fancy on the Pi side . But this will only work if you connect the same power supply to both ports. If it's not the same power supply, you could damage the supply's. (The pi will probably be fine)

Laurens

[Laurens-wuyts]

I think the only Schematic that's ever been published was for the Pi1 boards, and those led to various "compatible" clones that weren't really compatible and detracted from the Foundations aims.

I also think the schematics of the compute module are available.

Laurens