LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Custom CM4 Board- no hdmi no console out

Fri May 14, 2021 5:42 pm

Hi,
we have a custom CM4 carrier board.
a) CM4 with eMMC (Raspberry Pi OS)
In the custom board, have used HDMI0. So we've added

Code: Select all

framebuffer_priority = 2

in the config.txt file along with USB enable.
CM4 connects to a mobile phone hotspot but not able to ping.
We do not see anything on HDMI n neither access on console.
The I/P Voltage level on cm4 and output are fine on Both carrier Board
what more can be looked into?
Tested with IO Board and works fine.

b) CM4 without eMMC
with Raspberry Pi OS Lite
Act LED stays on
doesn't connect to a hotspot.
Works well in IO Board.
All the voltage level looks good SD_PWR is 3V3.

Thanks.

dp11
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 520
Joined: Thu Dec 29, 2011 5:46 pm

Re: Custom CM4 Board- no hdmi no console out

Fri May 14, 2021 6:03 pm

I think it would be worth posting your schematics and PCB layout.

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Fri May 14, 2021 6:46 pm

Can I send the PCB files privately?


For schematic, you can find here
viewtopic.php?f=98&t=303697&p=1818485#p1818485

The Ethernet section was missing from the previous post
https://drive.google.com/file/d/1FQd_KA ... sp=sharing

dp11
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 520
Joined: Thu Dec 29, 2011 5:46 pm

Re: Custom CM4 Board- no hdmi no console out

Fri May 14, 2021 7:13 pm

By connect to mobile hot spot what do you mean ?

Also are these the actual circuits that match your board ? or have you made any changes ?

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Fri May 14, 2021 7:24 pm

through phone's network, I mean connected on the same WiFi network as mobile device.
Yes the schematic is as-is no changes

dp11
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 520
Joined: Thu Dec 29, 2011 5:46 pm

Re: Custom CM4 Board- no hdmi no console out

Fri May 14, 2021 7:38 pm

So Just to confirm the HDMI output works on the CM4IO board but not your board.? If so it is almost certainly either a pinout issue with the HDMI connector or a PCB routing issue.

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 1:09 am

I checked again I don't see anything wrong with schematic or PCB routing attaching the image for reference

HDMI Layout-I
https://drive.google.com/file/d/1QfpHPW ... sp=sharing

HDMI Layout-II
https://drive.google.com/file/d/1UtKcOW ... sp=sharing

HDMI Layout-III
https://drive.google.com/file/d/1HMV50l ... sp=sharing

HDMI Schematic- Connector and CM4
https://drive.google.com/file/d/1tBAH2v ... sp=sharing

HDMI Schematic and CM4IO
https://drive.google.com/file/d/1IrJirQ ... sp=sharing

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 1:13 am

dp11 wrote:
Fri May 14, 2021 7:38 pm
So Just to confirm the HDMI output works on the CM4IO board but not your board.?
Yes, HDMI works on IO Board But UART Console doesn't work on both.
Config.txt

Code: Select all

# For more options and information see
# http://rpf.io/configtxt
# Some settings may impact device functionality. See link above for details

# uncomment if you get no picture on HDMI for a default "safe" mode
#hdmi_safe=1

framebuffer_priority = 2

# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
#disable_overscan=1

# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16

# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720

# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1

# uncomment to force a specific HDMI mode (this will force VGA)
#hdmi_group=1
#hdmi_mode=1

# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2

# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4

# uncomment for composite PAL
#sdtv_mode=2

#uncomment to overclock the arm. 700 MHz is the default.
#arm_freq=800

# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on

# Uncomment this to enable infrared communication.
#dtoverlay=gpio-ir,gpio_pin=17
#dtoverlay=gpio-ir-tx,gpio_pin=18

# Additional overlays and parameters are documented /boot/overlays/README

# Enable audio (loads snd_bcm2835)
dtparam=audio=on

[pi4]
# Enable DRM VC4 V3D driver on top of the dispmanx display stack
dtoverlay=vc4-fkms-v3d
max_framebuffers=2

[all]
#dtoverlay=vc4-fkms-v3d

dtoverlay=dwc2,dr_mode=host

dp11
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 520
Joined: Thu Dec 29, 2011 5:46 pm

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 4:04 am

I assume l the next layer on the PCB is a completely solid ground plane under the hdmi traces? All I assume the track and gap is correct for 100ohms?

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 5:21 am

Yes, 2nd Layer is Solid ground plane.
Yes, the trace width and gap are correct for 100 Ohm.

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 6:48 am

dp11 wrote:
Sat May 15, 2021 4:04 am
I assume l the next layer on the PCB is a completely solid ground plane under the hdmi traces? All I assume the track and gap is correct for 100ohms?
on the 2nd Board, ACT led is always on

dp11
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 520
Joined: Thu Dec 29, 2011 5:46 pm

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 8:46 am

You haven't routed the ESD diodes correctly. You need to route the nc pins to the diodes see page 10 of the ESD diode datasheet. See how the ESD diodes are routed on the CM4IO board for the ethernet socket for examples.

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 9:27 am

Yeah, should've connected the NC pins to the diode.
But still I should be able to connect through uart console ?

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 10:38 am

I've checked again on the Hardware checklist of the CM4 datasheet.
a) with eMMC,
Everything is fine until step 10 on the hardware checklist and not able to see anything on the console and have an Ethernet cable connected, the Ethernet LED's on the Pi not lighting up which means pi is not booted?
b) with SD Card,
Normal until step 9 and act led lights up always.

dp11
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 520
Joined: Thu Dec 29, 2011 5:46 pm

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 11:12 am

I'm not sure I've seen the PCB layout. Its hard to guess what might be wrong especially given you say it works on the CM4IO board.

LakshmiN
Posts: 52
Joined: Mon May 13, 2019 7:50 am

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 12:23 pm

Can I send the files privately?

dp11
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 520
Joined: Thu Dec 29, 2011 5:46 pm

Re: Custom CM4 Board- no hdmi no console out

Sat May 15, 2021 1:34 pm

you might want to try one of the design partners https://www.raspberrypi.org/for-industr ... -partners/

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