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Interfacing (DSI, CSI, I2C, etc.) • CM5/Pi5 console on GPIO14/15 - can only receive on PC but not send data to Pi

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On a Pi5 and CM5 DUTs I'm trying to have a console on GPIO14/15.

I've enabled it like
in config.txt

Code:

enable_uart=1
in cmdline.txt

Code:

earlycon=pl011,0x107d001000,115200n8 console=serial0,115200 console=tty1
in rpi-eeprom-config I did not change anything hence

Code:

BOOT_UART=1
After a reboot checking what I have I see

Code:

pi@newpi5:~ $ ls -l /dev/ttyAMA0crw-rw---- 1 root dialout 204, 64 Aug  1 09:02 /dev/ttyAMA0pi@newpi5:~ $ sudo stty -F /dev/ttyAMA0 115200
I'm then looking at the system config and it shows GPIO14/15 configured for UART

Code:

cmdline.txt-----------reboot=w coherent_pool=1M 8250.nr_uarts=1 pci=pcie_bus_safe cgroup_disable=memory numa_policy=interleave nvme.max_host_mem_size_mb=0  numa=fake=8 system_heap.max_order=0 smsc95xx.macaddr=D8:3A:DD:C0:03:23 vc_mem.mem_base=0x3fc00000 vc_mem.mem_size=0x40000000  earlycon=pl011,0x107d001000,115200n8 trace_event=i2c console=ttyAMA0,115200 console=tty1 root=PARTUUID=08983b46-02 rootfstype=ext4 fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles cfg80211.ieee80211_regdom=DEpin configuration----------------- 0: a3    pu | hi // ID_SDA/GPIO0 = SDA0 1: a3    pu | hi // ID_SCL/GPIO1 = SCL0 2: no    pu | -- // GPIO2 = none 3: no    pu | -- // GPIO3 = none 4: no    pu | -- // GPIO4 = none 5: no    pu | -- // GPIO5 = none 6: no    pu | -- // GPIO6 = none 7: no    pu | -- // GPIO7 = none 8: no    pu | -- // GPIO8 = none 9: no    pd | -- // GPIO9 = none10: no    pd | -- // GPIO10 = none11: no    pd | -- // GPIO11 = none12: no    pd | -- // GPIO12 = none13: no    pd | -- // GPIO13 = none14: a4    pn | hi // GPIO14 = TXD015: a4    pu | hi // GPIO15 = RXD016: no    pd | -- // GPIO16 = none17: no    pd | -- // GPIO17 = none18: no    pd | -- // GPIO18 = none19: no    pd | -- // GPIO19 = none20: no    pd | -- // GPIO20 = none21: no    pd | -- // GPIO21 = none22: no    pd | -- // GPIO22 = none23: no    pd | -- // GPIO23 = none24: no    pd | -- // GPIO24 = none25: no    pd | -- // GPIO25 = none26: no    pd | -- // GPIO26 = none27: no    pd | -- // GPIO27 = none
sending below message

Code:

pi@newpi5:~ $ echo hello > /dev/ttyAMA0pi@newpi5:~ $ echo hello > /dev/ttyAMA0pi@newpi5:~ $ echo hello > /dev/ttyAMA0pi@newpi5:~ $ 
results in the output like shown below on my PC

Code:

[ 4425.989725] reboot: Restarting system                                                                                                                        Debian GNU/Linux 12 newpi5 ttyAMA0                                                                                                                              My IP address is 192.168.178.45 2a02:2455:1c9a:700:b258:d5fe:1eef:73d2                                                                                          newpi5 login: hello                                                             hello                                                                           hello   
but the problem I'm facing is that I can only receive on the PC, but not send anything back to the Pi; I.e. pressing any key in the minicom window results in nothing.
What am I doing wrong here or what's missing?

Statistics: Posted by aBUGSworstnightmare — Fri Aug 01, 2025 8:31 am — Replies 4 — Views 191



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