====== Hardware ======

PI Compute Board:
  * RPI-CM4Lite-R1-3: https://www.berrybase.de/raspberry-pi/raspberry-pi-computer/compute-modules/raspberry-pi-compute-module-4-4gb-ram-lite-wlan-43-bt
       * With Heatsink (https://www.pollin.de/p/joy-it-kuehlkoerperset-fuer-raspberry-pi-810822)
Board: 
  * Wavesahre CM4-IO-BASE-B https://www.waveshare.com/wiki/CM4-IO-BASE-B
WIFI Board:
  * R11e-2HPnD https://mikrotik.com/product/R11e-2HPnD
Measurement devices
  * USB Power Meter : www.coowootech.com/de/coowoo-usb-digital-power-meter-tester-multimeter-current-and-voltage-monitor-dc-51a-30v-amp-voltage-power-meter-test-speed-of-chargers-cables-capacity-of-power-banks-black.html
  * It measures (+-1% Error)
       * Watts
       * WattHours 
{{ ::IMG_20210502_160107.jpg?400 |}}
  * PI4 Internal CPU Thermometer
  * Multimeter: AM-550-EU PTC Temperature for Wifi Temperature Measurements
      * The temperature of the wifi module by placing the ptc at the heatsink of the wifi module
      * Not highly accurate, but should give a indication
Lab Power source
  * Quatpower LN-3003 

====== Software ======

==== Reduce power usage of CM4 ====

**no bluetooth**
  * config.txt
  * dtoverlay=disable-bt

**no wifi**
  * config.txt
  * dtoverlay=disable-wifi

**no eth**
  * https://www.raspberrypi.org/forums/viewtopic.php?t=290965
  * dtoverlay=noeth

**reduce cpu freq**
  * config.txt
  * arm_freq=500
  * arm_freq_min=200
  * arm_freq_max=1000

**leds**
  * config.txt
  * dtparam=act_led_trigger=none
  * dtparam=act_led_activelow=off
  * dtparam=pwr_led_trigger=none
  * dtparam=pwr_led_activelow=off

**no audio**
  * config.txt
  * dtparam=audio=off

**no USB**
  * disabled by default @ CM4 for powersaving
  * https://www.jeffgeerling.com/blog/2020/usb-20-ports-not-working-on-compute-module-4-check-your-overlays

==== Testsoftware ==== 

**Camerasoftware**
<code>
pi@testi:~$ cat test_dual_cam.py 
import time
from datetime import datetime

import picamera
c0 = picamera.PiCamera(camera_num=0)
c0.resolution = (3280,2464)
c0.exposure_mode = "beach"
c1 = picamera.PiCamera(camera_num=1)
c1.resolution = (3280,2464)
c1.exposure_mode = "beach"

while True:
    pic_stamp = datetime.now()
    filename = pic_stamp.strftime("%Y-%m-%dT%H-%M-%S.%f") + "_a" + ".jpg"
        
    start = time.time()
    c0.capture(filename, format='jpeg', quality=95, thumbnail=None, use_video_port=False)
    end = time.time()
    duration = end-start
    print("[Photo0] image capture took [s]:{0:8.3f}".format(duration))

    filename = pic_stamp.strftime("%Y-%m-%dT%H-%M-%S.%f") + "_b" + ".jpg"
    start = time.time()
    c1.capture(filename, format='jpeg', quality=95, thumbnail=None, use_video_port=False)
    end = time.time()
    duration = end-start
    print("[Photo1] image capture took [s]:{0:8.3f}".format(duration))
    
</code>

**WifiSoftware**
  * WIFIBroadcast : https://github.com/booo/wifibroadcast/
  * Using 30dbm permanent TX Power @ MCS0
<code>
cat /dev/zero  | sudo ./tx wlan0 
</code>

====== Tests ======

==== Test 1 - 2 cameras ====


{{ ::IMG_20210502_160159.jpg?400 |}}
{{ ::img_20210502_160043.jpg?400 |}}

^ Testmode      ^ Time (h) ^ Power usage (Wh)  ^ Power usage (W) ^ CPU Temp (°C) ^
| IDLE          |  0:00    |   2.488           |   1.095         |  38           |
| use 2 cameras |  0:00    |   2.489           |   1.8           |  39           |   
| use 2 cameras |  0:15    |   2.95            |   1.8           |  43.8         |   
| use 2 cameras |  0:30    |   3.4             |   1.8           |  44.3         |   

Using the power usage in Wh a **mean power of ~1.8W** is needed when using 2 cameras.

==== Test 2 - 2 cameras + Wifi ==== 

{{ ::IMG_20210503_000548.jpg?400 |}}

^ Testmode      ^ Time (h) ^ Power usage (Wh)  ^ Power usage (W) ^ CPU Temp (°C) ^ WIFI Temp (°C) ^
| IDLE          |  0:00    |   -           |   1.7         |  43.8           |  30           |
| use 2 cameras |  0:00    |   -           |   2.4         |  43.8           |  30           |
| WIFI          |  0:00    |   -           |   2.65         |  43.8          |  30           |
| use 2 cameras + WIFI |  0:00    |   4.83       |   3.2           |  43.8           |   30           | 
| use 2 cameras + WIFI |  0:15    |   5.666       |   3.2           |  52.0           |   48           | 
| use 2 cameras + WIFI |  0:30    |   6.52       |   3.2           |  53.0           |   50           | 

Using the power usage in Wh a **mean power of ~3.38W** is needed when using 2 cameras + wifibroadcast.

==== Test 3 - Wifi ==== 

As it turned out that the radio power amplifier was not connected in test #2, i reran the test. Power is provided by the laboratory power source @ 12.3V + DCDC Converter @ 5V for the cm4 board. 

**NOTE:** The sligtly incread Idle power usage is due to the additional DCDC converter, and the powermeasurement BEFORE this converter.

^ Testmode  ^ Time (h) ^ Power usage (W) ^ CPU Temp (°C) ^ WIFI Temp (°C) ^
| IDLE |  0:00    | 2.3      |  34.5          |  27           |
| WIFI |  0:01    | 5.78     |  36.5          |  29           |
| WIFI |  0:11    | 5.78     |  46.7           |   58           | 
| WIFI |  0:21    | 5.78     |  51.0           |   62           | 
| WIFI |  0:30    | 5.78     |  51.0           |   63           |