Rock64 v3 - POE

[mcerveny]

POE implementation was successful. POE PD 5V RT9400 ($4, 14mm width to attach in common case) + power button ML6-H1S12BVA ($1.5) + case EM-RasPI B+ basic ($6) + silicone thermal pads with adhesive to attach/cool POE (1mm/3mm) + cables and connectors + some passives = ~$13.

Implementation notes:

• * Power button LED with 100 Ω resistor to 5V (20mA/3V LED forward voltage). Power button GND switch to PWRON connector (with internal pullup in RK805).
  
• * Additional LOAD 120 Ω resistor between GND-5V (40mA) (or add more LEDs) to get minimum required power draw from POE PD with power off ROCK64 (very unlikely state). 60mA (20ma+40ma) generates power ripple about 0.2V and switching frequency about 2000Hz, officially RT9400 need at least 200mA (with low ripple). With Additional POE capacitor (see below) it works event without LOAD resistor.
  
• * Additional POE 270 kΩ resistor between RT9400 ADJ and -VDC (GND) to adjust regulated voltage from ~5.0V to ~5.1V.
  
• * Additional POE 470 µF/16V capacitor with low ESR between +VDC and -VDC (GND) (Hitano EXR and not from SYK).
  
• * POE switch reports 2.1W/44mA when booted idle (CPU 400MHz, temperature 50C), 5.2W/110mA when stressed ("stress --cpu 4 --vm 2 --vm-bytes 128M", CPU 1296MHz, temperature up to 90C in assembled case) without any USB device connected (booted from SDcard) and 0.2W/6mA when power off ROCK64.
  
• * Estimated 1A is available to USB devices.
  
• * Test with HDMI connected, 2xUSB mouse+keyboard and USB3 HDD (Samsung EVO (rated 1200 mA) connected over AXAGON USB to SATA adapter 6G), POE switch reports maximum 8.9W/188mA.
  
  Code:

  # lsusb -t
/:  Bus 05.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 5000M
    |__ Port 1: Dev 2, If 0, Class=Mass Storage, Driver=uas, 5000M
/:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci-hcd/1p, 480M
/:  Bus 03.Port 1: Dev 1, Class=root_hub, Driver=ohci-platform/1p, 12M
    |__ Port 1: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ehci-platform/1p, 480M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc2/1p, 480M
    |__ Port 1: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
    |__ Port 1: Dev 2, If 1, Class=Human Interface Device, Driver=usbhid, 1.5M
# lsusb -v 2>/dev/null | grep MaxPower | grep -v " 0mA"
    MaxPower              896mA
    MaxPower              100mA
    MaxPower              100mA

# ### IDLE reported from switch - average 3.7W/77mA

#  while true; do cat /sys/devices/virtual/thermal/thermal_zone0/temp /sys/devices/system/cpu/cpufreq/policy0/scaling_cur_freq; iostat 1 2 | tail -2;  done
58181
408000
sda               0.00         0.00         0.00          0          0

# ### DD reported from switch - average 6.8W/144mA

# dd if=/dev/sda of=/dev/null bs=1024k
#  while true; do cat /sys/devices/virtual/thermal/thermal_zone0/temp /sys/devices/system/cpu/cpufreq/policy0/scaling_cur_freq; iostat 1 2 | tail -2;  done
69230
1296000
sda            2435.00    311552.00         0.00     311552          0

# ### DD+stress reported from switch - average 7.6W/159mA and max 8.9W/188mA
# ### less stress to allow some CPU for USB3/DD processing

# stress --cpu 1 --vm 1 --vm-bytes 128M
#  while true; do cat /sys/devices/virtual/thermal/thermal_zone0/temp /sys/devices/system/cpu/cpufreq/policy0/scaling_cur_freq; iostat 1 2 | tail -2;  done
88076
1296000
sda            1986.00    254208.00         0.00     254208          0

Actual versions of POE (~ $4 (poe) + $1 (capacitor+connectors)) without poweron button for RaspberyPI 4 (Rock64 v3 compatible).

The last post. Farewell.