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02-reduce-power-consumption.md

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Reduce power consumption

When the Rasberry PI uses too much power, the WaveShare Hat does not connect the GSM network.

Turn off USB/LAN and HDMI output

The following show the difference between the old (red) and adapted text file (green) as generated by the command diff --color -u old_file new_file. The file to change are chown in the second line. New lines start with + (green) and removed/replaced lines start with - (red). The markers (+/-/@) should not be added to the file.

--- /etc/rc.local.bak	2023-01-22 19:47:55.906202807 +0000
+++ /etc/rc.local	2023-01-22 19:49:30.933060657 +0000
@@ -17,4 +17,11 @@
   printf "My IP address is %s\n" "$_IP"
 fi

+# Turn off USB/LAN
+# https://raspberrypi-guide.github.io/electronics/power-consumption-tricks
+echo '1-1' |sudo tee /sys/bus/usb/drivers/usb/unbind
+
+# Turn off HDMI output
+sudo /opt/vc/bin/tvservice -o
+
 exit 0

Please make a copy for thed file to be edited first and check the differences:

sudo cp /etc/rc.local /etc/rc.local.bak
sudo nano /etc/rc.local
diff --color -u /etc/rc.local.bak /etc/rc.local

The output of diff should match to the difference shown before.

Disable BlueTooth

Run these commands to disable BlueTooth:

sudo systemctl disable hciuart.service
sudo systemctl disable bluetooth.service

Down-clock CPUs

As before, make a back-up copy, edit the file and finaly review the changes with:

sudo cp /boot/config.txt /boot/config.txt.bak
sudo nano /boot/config.txt
diff --color -u /boot/config.txt.bak /boot/config.txt

--- /boot/config.txt.bak	2023-02-18 15:30:02.000000000 +0000
+++ /boot/config.txt	2023-02-21 20:28:54.000000000 +0000
@@ -78,7 +78,14 @@
 
 [pi4]
 # Run as fast as firmware / board allows
-arm_boost=1
+arm_boost=0
 
 [all]
+enable_uart=1
+
+# https://www.foxplex.com/sites/raspberry-pi-over-und-underclocking/
+arm_freq=700
+core_freq=250
+core_freq_min=75
+sdram_freq=400
+over_voltage=0

Just 1 CPU core

How many CPU core does the Rassberry Pi have? Run the following command:

cat /proc/cpuinfo

To reduce the power consumption, limit the CPU cores to 1.

  • Add maxcpus=1 to the file /boot/cmdline.txt before root.
  • If the file contains console=serial0,115200, then you should remove it.

Do not change the identifier following root=PARTUUID= or anything else.

As before, make a back-up copy, edit the file and finaly review the changes with:

sudo cp /boot/cmdline.txt /boot/cmdline.txt.bak
sudo nano /boot/cmdline.txt
diff --color -u /boot/cmdline.txt.bak /boot/cmdline.txt

For example, my changes looked like this.

--- /boot/cmdline.txt.bak	2023-01-22 21:01:02.000000000 +0000
+++ /boot/cmdline.txt	2023-01-22 21:02:04.000000000 +0000
@@ -1 +1 @@
-console=tty1 root=PARTUUID=a999dc5f-02 rootfstype=ext4 fsck.repair=yes rootwait
\ No newline at end of file
+console=tty1 maxcpus=1 root=PARTUUID=a999dc5f-02 rootfstype=ext4 fsck.repair=yes rootwait

Reboot

To reboot the Rasberry pi use the following command (you will need to reconnect via SSH, after the reboot process is finished):

sudo reboot