otg service needs to run before serial-getty

README.md

@@ -8,11 +8,13 @@ Scripts and documentation for setting up a Raspberry Pi (Zero W 1 or 2) for use
 1. [Solder the GPIO header pins](solder-gpio.md)
 1. [Gadget Mode to setup a serial connection over USB](gadget.md)
 1. [Marcel's script on github to show the IP address on the OLED screen](https://github.com/mkyas/cpsy-display-ip)
+1. Install Blinka by following the guide [CircuitPython Libraries on Linux and Raspberry Pi](https://learn.adafruit.com/circuitpython-on-raspberrypi-linux/installing-circuitpython-on-raspberry-pi)]
 
 ## RU student-only guides at ROB-IOT
 - [Starting on Raspberry Pi Zero](https://reykjavik.instructure.com/courses/6589/pages/starting-on-raspberry-pi-zero-w)
 
 ## References and Links
+- [Sparkfun GPIO pinout](https://cdn.sparkfun.com/assets/learn_tutorials/6/7/6/PiZero_1.pdf)
 - [Guide to creating ssh keys](https://pimylifeup.com/raspberry-pi-ssh-keys/)  Of note, this guide is a little dated as it suggests using RSA keys and many people are moving toward EDCSA keys.
 - [Raspberry Pi Connect](https://connect.raspberrypi.com)
     - [Setting up Raspberry Pi Connect](https://www.raspberrypi.com/documentation/services/connect.html)	
@@ -29,6 +31,7 @@ Scripts and documentation for setting up a Raspberry Pi (Zero W 1 or 2) for use
 
 ## TODO
 - Finding the Pi using `nmap` or `arp`
+- Create a interface HAT that makes it easy to attach to a digital analyzer (v207) and an Analog Discovery
 # Some Tricks
 
 Here is a page of tricks we have discovered that may involve advanced techniques.

Scripts/serial-ether-gadget.service

@@ -1,6 +1,7 @@
 [Unit]
 Description=Serial and Ethernet over OTG USB
-After=systemd-user-sessions.service
+#After=systemd-user-sessions.service
+Before=serial-getty@ttyGS0.service
 [Service]
 ExecStart=/root/rover-pi/Scripts/gadget.sh
 [Install]

bluetooth.md

@@ -0,0 +1,79 @@
+# Bluetooth on the Raspberry Pi Zero W (1 or 2)
+The Zero W series has Bluetooth capability because of the Wifi chip on the board.
+**Warning:  This is a work in progress!!!**
+
+# Reference
+- "Exploring Raspberry Pi" by Derek Molloy pg 537-544
+- [Connecting to a Headless Raspberry Pi using Bluetooth](https://medium.com/@tomw3115/connect-to-a-headless-raspberry-pi-using-bluetooth-0e61c05e1b68)
+- https://github.com/sorah/bluetooth-getty
+- [Use dbus insteadd of sdptool](https://linuxvox.com/blog/bluez-adding-services-attributes-and-profiles-without-sdptool-command/)
+
+# Getting Bluetooth working
+1. Login to the pi via a USB-serial port or monitor-keyboard-mouse.  Configuring bluetooth can sometimes kick you off the wifi.
+1. Tell `rfkill` to unblock bluetooth.  Perhaps this is a security thing?
+```
+sudo rfkill unblock bluetooth
+```
+1. Restart the bluetooth service and check it's status
+```
+sudo systemctl restart bluetooth
+sudo systemctl status bluetooth
+```
+1. Figure out the address using `hcitool`
+```
+hcitool dev
+```
+1. If you have a laptop set to be discoverable, you can check if bluetooth is working
+```
+hcitool scan
+```
+1. You can then query that device for what services it offers
+```
+sdptool browse ADDRESS
+```
+1. Now we want to make the Pi discoverable to our phone, tablet, or laptop
+```
+sudo hciconfig hci0 piscan
+sudo hciconfig hci name RaspberryPi
+```
+1. A Serial Port Profile(SPP) is needed for our serial port
+```
+sudo sdptool add SP
+```
+1. For some reason, we have to put the bluetooth daemon in compatibility mode.  (True as of 2016-2026 --foley).  Find the line with `ExecStart` and put `--compat` at the end
+```
+sudo nano /lib/systemd/system/bluetooth.service
+```
+1. Test the SPP is setup
+
+```
+sudo sdptool browse local
+```
+1. Time to pair it with a device
+```
+sudo bluetoothctl
+discoverable on
+agent on
+pairable on 
+scan on
+```
+and once you have paired it
+```
+discoverable off
+exit
+```
+
+1. If this works, you can install the `bluetooth.services` and `rfcomm.service` files to automate some of this setup.
+```
+sudo cp bluetooth.service /etc/systemd/system/bluetooth.target.wants/.
+sudo cp rfcomm.service /etc/systemd/system/.
+sudo systemctl daemon-reload
+sudo systemctl enable rfcomm
+sudo reboot
+
+```
+
+
+
+# Discussion
+Apparently Bluez's `sdptool` is now depricated and they are telling people to use this new GATT via `busctl` or `dbus-send`. [linuxvox article on depricated sdptool](https://linuxvox.com/blog/bluez-adding-services-attributes-and-profiles-without-sdptool-command/)

imager.md

@@ -44,3 +44,12 @@ We don't have many monitors and keyboards in V207 for students to use, so we wil
 ![imager-writeimage-verifying.png](Graphics/imager-writeimage-verifying.png)
 1. The process is complete!  Now you can [connect to your pi](connect.md)
 ![imager-complete.png](Graphics/imager-complete.png)
+1. Take the SD card and put it into your pi.
+1. When you first boot it, it can take 10 minutes to finish configuring itself.  Usually when the LED stops blinking for at least 30 seconds, it is done.
+
+## Connecting using Raspberry Pi Connect
+1. Login to https://connect.raspberrypi.com if you haven't already
+1. Look at the list of devices, find the one you want, and click on "Connect"
+![connect-devices.png](Graphics/connect-devices.png)
+1. A remote shell window will pop up
+![connect-shell.png](Graphics/connect-shell.png)

imu.md

@@ -0,0 +1,13 @@
+# The Intertial Measurement Unit
+
+As of 2025, we started using an AliExpress version of https://wolles-elektronikkiste.de/en/icm-20948-9-axis-sensor-part-i
+
+This has an unmarked jumper on the back.  Joe believes that it shorts the VDDIO and VDD pins in order to allow it to be used with 1.8V devices.
+
+Marcel has tested that the pads connect to both of those pins.
+
+The IMU runs on 1.8V, but our Pi has GPIO voltages of 3.3V.  Marcel reports that students in 2025 had no problem using it as long as AD0 and NCS were connected to VDD.
+According to the specification, the maximum pin voltage is VDDIO+0.5, which would put it at 2.3, a whole volt below 3.3.  On his board, he connected the pins to 3.3V though a 10K resistor to protect it from overcurrent.
+
+For I2C at least, it appears that we are saved by the fact that it is open-drain.  Each device communicates to the master by pulling lines low, which should work with both voltages.
+

lgpio/blink.py

@@ -0,0 +1,19 @@
+#!/usr/bin/python
+# From https://raspberry.tips/en/raspberrypi-tutorials/raspberry-pi-gpio-python
+import lgpio
+import time
+
+# Open GPIO chip (0 = /dev/gpiochip0, on Pi 5 gpiochip4 also possible)
+h = lgpio.gpiochip_open(0)
+
+try:
+    lgpio.gpio_claim_output(h, 18)   # GPIO18 (pin 12) as output (MOTA1)
+
+    for _ in range(5):
+        lgpio.gpio_write(h, 18, 1)   # HIGH
+        time.sleep(0.5)
+        lgpio.gpio_write(h, 18, 0)   # LOW
+        time.sleep(0.5)
+    
+finally:
+    lgpio.gpiochip_close(h)          # Always close!

lgpio/motor-test.py

@@ -0,0 +1,34 @@
+#!/usr/bin/python
+# This test assumes you are trying to control a motor through a DRV8833 motor
+# controller chip.  This general approach should work for other motors as well.
+import lgpio
+import time
+
+# pin assignments
+gpio_pwm = 18  #MOTA1
+gpio_reverse = 16 #MOTA2
+gpio_notsleep = 24 #MSLEEP
+# parameters
+pwm_freq = 1000
+
+
+h = lgpio.gpiochip_open(0)
+try:
+    lgpio.gpio_claim_output(h, gpio_reverse)
+    lgpio.gpio_claim_output(h, gpio_notsleep)
+    lgpio.gpio_write(h, gpio_reverse, 0)   # low on reverse pin to turn off h-bridge MOTA2
+    lgpio.gpio_write(h, gpio_notsleep, 1)   # high on /sleep to enable both h-bridges
+    
+    while True:
+        for pwm_level in range(0,100):
+            lgpio.tx_pwm(h, gpio_pwm, pwm_freq, pwm_level)
+            pwm_level += 10
+            time.sleep(0.05)
+        for pwm_level in range(100,0,-1):
+            lgpio.tx_pwm(h, gpio_pwm, pwm_freq, pwm_level)
+            pwm_level += 10
+            time.sleep(0.05)
+
+finally:
+    lgpio.gpio_write(h, gpio_notsleep, 1)   # high on /sleep to disable    
+    lgpio.gpiochip_close(h)          # Always close!

lgpio/pwm-test.py

@@ -0,0 +1,25 @@
+#!/usr/bin/python
+# From https://raspberry.tips/en/raspberrypi-tutorials/raspberry-pi-gpio-python
+import lgpio
+import time
+
+# Open GPIO chip (0 = /dev/gpiochip0, on Pi 5 gpiochip4 also possible)
+h = lgpio.gpiochip_open(0)
+# Hardware PWM on GPIO18 (pin 12) must be PWM-capable
+pwm_pin = 18
+pwm_freq = 1000
+try:
+    while True:
+        for pwm_level in range(0,100):
+            lgpio.tx_pwm(h, pwm_pin, pwm_freq, pwm_level)
+            pwm_level += 10
+            time.sleep(0.05)
+        for pwm_level in range(100,0,-1):
+            lgpio.tx_pwm(h, pwm_pin, pwm_freq, pwm_level)
+            pwm_level += 10
+            time.sleep(0.05)
+
+            
+finally:
+    lgpio.tx_pwm(h, pwm_pin, 0, 0)   # Stop PWM
+    lgpio.gpiochip_close(h)          # Always close!

pwm.md

@@ -0,0 +1,61 @@
+# Getting the PWM working
+
+The Raspberry Pi zero (1 and 2) have 2 PWM peripherals, allowing you to pulse pins without the CPU doing any additional work.  This is particuarly useful for controlling motor speeds when connected to a motor driver/H-bridge chip.
+
+
+# References
+- [CircuitPython Libraries on Linux and Raspberry Pi](https://learn.adafruit.com/circuitpython-on-raspberrypi-linux/installing-circuitpython-on-raspberry-pi)
+- [Raspberry Pi Official Overlays information (github)](https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README)
+    - Line 4235 starts the description of the "pwm" overlay configuration
+- [Adding Basic Audio Ouput to Raspberry Pi Zero](https://learn.adafruit.com/adding-basic-audio-ouput-to-raspberry-pi-zero/pi-zero-pwm-audio)
+- [CircuitPython pwmio documentation](https://docs.circuitpython.org/en/latest/shared-bindings/pwmio/index.html)
+
+
+# Important Points
+1. The `gpio` program is no longer available.  It has been replaced with `pinctrl` which works a little differently.
+1. The Blinka/CircuitPython interface uses `lgpio` to do hardware PWM on the pins.  This requires the `pwm-2chan` overlay to be setup correctly, which it's documented procedure does.  Details on relevant pins on line 4267 of the [overleays README](https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README)
+
+# Discussion
+
+
+My raspberry pi zero W 2 wasn't working reliably with the PWM.
+
+The `gpio` command has been depricated and is now replaced by the `pinctrl` commend.  Running it did not list any PWM0 on any of the pins, which was concerning.
+
+[This forum post](https://forums.raspberrypi.com/viewtopic.php?t=388352) indicated the need for a `pwm-2chan` device tree overlay to get it to show up.  After adding `dtoverlay=pwm-2chan` to the `config.txt`:
+
+```
+$ pinctrl
+ 0: ip    -- | hi // ID_SDA/GPIO0 = input
+ 1: ip    -- | hi // ID_SCL/GPIO1 = input
+ 2: a0    -- | hi // GPIO2 = SDA1
+ 3: a0    -- | hi // GPIO3 = SCL1
+ 4: op -- -- | hi // GPIO4 = output
+ 5: ip    -- | hi // GPIO5 = input
+ 6: ip    -- | hi // GPIO6 = input
+ 7: op -- -- | hi // GPIO7 = output
+ 8: op -- -- | hi // GPIO8 = output
+ 9: a0    -- | lo // GPIO9 = SPI0_MISO
+10: a0    -- | lo // GPIO10 = SPI0_MOSI
+11: a0    -- | lo // GPIO11 = SPI0_SCLK
+12: ip    -- | lo // GPIO12 = input
+13: ip    -- | lo // GPIO13 = input
+14: ip    -- | lo // GPIO14 = input
+15: ip    -- | hi // GPIO15 = input
+16: ip    -- | lo // GPIO16 = input
+17: ip    -- | lo // GPIO17 = input
+18: a5    -- | lo // GPIO18 = PWM0
+19: a5    -- | lo // GPIO19 = PWM1
+```
+
+Which looks much better.
+There is a pwm chip `in /sys/class/pwm`
+
+After running the `lgpio/pwm-test.py`
+the pin is back to being listed as an input, so I'm confused.
+The PWM pin (under load) did the right values.  Without a load on the Analog Discovery 2, I just saw noise.
+
+I commented out `dtoverlay=pwm-2chan` and `lgpio/pwm-test.py` worked.
+The pwm chip is missing from `/sys/class/pwm` so I'm guess that's not needed.
+
+