Problems connecting to pi 3 via ttl (cp2102)

Question

I'm following raspberrypi.org THE RASPBERRY PI UARTS guide, trying to connect from mac 10.13.6 High Sierra to Pi 3 using screen.

I had to disable system integrity protection on mac (high sierra) to get the cp1202 kext loaded. Once i did that, i was able to see the /dev/cu.SLAB_USBtoUART. I tried connecting using screen, but saw only garbage characters. I have disabled hciuart service, disabled serial login shell (kinda odd, but that's what the guide suggests), still only seeing garbage.

To clarify, I'm trying to establish a serial connection from mac to PI, so i can get to PI's shell via screen (for example) from mac.

Any help is much appreciated!

cp2102 drivers I'm using

end of /boot/config.txt

# Additional overlays and parameters are documented 
/boot/overlays/README
# Disabling Bluetooth overlay
dtoverlay=pi3-disable-bt
dtoverlay=pi3-miniuart-bt

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

# NOOBS Auto-generated Settings:^M
hdmi_force_hotplug=1^M
enable_uart=1
gpu_mem=128

/boot/cmdline.txt

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p7 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

/lib/systemd/system/hciuart.service

[Unit]
Description=Configure Bluetooth Modems connected by UART
ConditionPathIsDirectory=/proc/device-tree/soc/gpio@7e200000/bt_pins
Before=bluetooth.service
After=dev-serial1.device

[Service]
Type=forking
ExecStart=/usr/bin/btuart

[Install]
WantedBy=multi-user.target

Answer 1

I have used a similar device (but not for some time). On the Mac this appears as /dev/tty.SLAB_USBtoUART. (AFAIK there is no need to disable SIP - the driver should be included).

I am not sure why you fiddled with the Bluetooth on the Pi but if you don't do this dev/serial0 should work (provided UART is enabled). See How do I make serial work on the Raspberry Pi3 , Pi3B+, PiZeroW

It is also unclear exactly what you expect hciuart.service to do (or if you have modified it) or indeed exactly what you are trying to do with the serial interface.

EDIT

If you want a Console use raspi-config to enable "login shell". You DO NOT need to fiddle with Bluetooth settings (the mini UART is more than capable of acting as a console).

I just tried on latest Raspbian - this gives login prompt, but there are a number of errors. I used the following.

screen /dev/tty.SLAB_USBtoUART 9600,cs8,-echo,-parenb,-echo

Unfortunately I do not know the cause, this used to work with older versions of Raspbian. I suspect a clocking error with the new governor.

EDIT2 I decided to do some further investigation. Using Serial Tools on the Mac (this is a free download from the Apps Store - and much friendlier than the arcane Screen) and minicom on the Pi serial communication seems to operate normally.

Any problems seem to only impact on the Serial Console.