Enable PWM for illumination LEDs on LL2+ and LL3 (#124)

This enables PWM on pins 13 and 18 to control the built-in dimmable
illumination LEDs on Limelight 2+ and 3. The symlink at
`/boot/config.txt` exists since that is the only path diozero checks for
pwm configuration right now, and should be removed once diozero is
updated to check `/boot/firmware/config.txt` or another source of PWM
information
([diozero#230](mattjlewis/diozero#230)).

Both LL2+ and LL3 have non-flickery LED dimming with these changes.

Needed to fix flickering LEDs in
[photonvision#2335](PhotonVision/photonvision#2335).

Author: thatcomputerguy0101

install_limelight.sh

@@ -23,6 +23,10 @@ chmod +x ./install.sh
 install -m 644 limelight/config.txt /boot/firmware/
 install -m 644 userconf.txt /boot/firmware/
 
+# link old config.txt location for diozero compatibility
+# TODO(thatcomputerguy0101): Remove this when diozero checks the new location
+ln -sf /boot/firmware/config.txt /boot/config.txt
+
 # install LL DTS
 dtc -O dtb limelight/gloworm-dt.dts -o /boot/firmware/dt-blob.bin
 

install_limelight3.sh

@@ -12,6 +12,13 @@ mkdir --parent /boot/firmware
 mount "${loopdev}p1" /boot/firmware
 ls -la /boot/firmware
 
+# Install our new config.txt with pwm overlay
+install -m 644 limelight3/config.txt /boot/firmware/
+
+# link old config.txt location for diozero compatibility
+# TODO(thatcomputerguy0101): Remove this when diozero checks the new location
+ln -sf /boot/firmware/config.txt /boot/config.txt
+
 # Add the one extra file for the LL3
 wget https://datasheets.raspberrypi.org/cmio/dt-blob-cam1.bin -O /boot/firmware/dt-blob.bin
 

limelight/config.txt

@@ -28,6 +28,9 @@ dtparam=audio=off
 
 max_framebuffers=2
 
+# Enable hardware PWM for LED control
+dtoverlay=pwm-2chan,pin=18,func=2,pin2=13,func2=4
+
 # Run in 64-bit mode
 arm_64bit=1
 

limelight3/config.txt

@@ -0,0 +1,47 @@
+# Automatically load overlays for detected DSI displays
+display_auto_detect=1
+
+# Automatically load initramfs files, if found
+auto_initramfs=1
+
+# Enable DRM VC4 V3D driver
+dtoverlay=vc4-kms-v3d
+max_framebuffers=2
+
+# Run in 64-bit mode
+arm_64bit=1
+
+# Disable compensation for displays with overscan
+disable_overscan=1
+
+# Enable hardware PWM for LED control
+dtoverlay=pwm-2chan,pin=18,func=2,pin2=13,func2=4
+
+[cm4]
+# Enable host mode on the 2711 built-in XHCI USB controller.
+# This line should be removed if the legacy DWC2 controller is required
+# (e.g. for USB device mode) or if USB support is not required.
+otg_mode=1
+
+[pi4]
+# Run as fast as firmware / board allows
+arm_boost=1
+
+[all]
+##############################################################
+### PHOTONVISION CAM CONFIG
+### Comment/Uncomment to change which camera is supported
+### Picam V1, V2 or HQ: uncomment (remove leading # ) from camera_auto_detect=1,
+### and comment out all following lines
+### IMX290/327/OV9281/Any other cameras that require additional overlays:
+### Comment out (add a # ) to camera_auto_detect=1, and uncomment the line for
+### the sensor you're trying to user
+
+camera_auto_detect=1
+
+# dtoverlay=imx290,clock-frequency=74250000
+# dtoverlay=imx290,clock-frequency=37125000
+# dtoverlay=imx378
+# dtoverlay=ov9281
+
+##############################################################