Raspbian Notes (Updated)

Setup

• Raspberry Pi 3 B+
• Raspbian Stretch Lite
• Logitech K375s (wireless via USB Unifying Receiver)
• Monitor (via HDMI)

Fixing Keyboard Annoyances

My Logitech K375s via the unifying receiver works properly except but some of the keys were all a-poopy, i.e.:

• Home and End cycle between ttys (just weird)
• Right-Control key would behave like a special character insert key (may be standard on non-US keyboards, I dunno)

No luck trying to change the locale/layout with raspi-config, but appending this to /etc/console-setup/cached_keyboard_setup.sh worked:

kbdrate -d 175 -r 200
loadkeys <<-EOT
    keymaps 0-255

    # make capslock another escape key
    keycode 50 = Escape

    # fix right control key
    keycode 100 = Control

    # fix home key
    keycode 105 = Left
    alt keycode 105 = Home

    # fix end key
    keycode 106 = Right
    alt keycode 106 = End
EOT

Pinning hardware device identifiers

I’m using the above-pictured TP-Link TL-WN7222N v3 USB Wi-Fi adapter which is capable of entering “monitor” mode. To actually put it into monitor mode though, you need a specialized rtl8188eu driver. After compiling, I manually tested and confirmed that it was working:

$ sudo insmod /lib/modules/4.19.66-v7++/kernel/drivers/net/wireless/8188eu.ko
$ sudo iwconfig wlan1 mode monitor

After rebooting, that same iwconfig command gave this error:

Error for wireless request "Set Mode" (8B06) :
    SET failed on device wlan1 ; Operation not supported.

Apparently the reboot reordered my wlan* devices: wlan0 (onboard) became wlan1 and wlan1 (USB) became wlan0. I’m assuming this is because the new 8188eu driver occurs before both the on-board’s brcmfmac and the default TP-Link’s r8188eu in lexical order?

I added this udev rule to pin the device ID to something predictable:

sudo tee /etc/udev/rules.d/tplink_wlan.rules <<< \
    'SUBSYSTEM=="net", ATTRS{idVendor}=="2357", ATTRS{idProduct}=="010c", NAME="tplink"'

To make sure the rule worked, I ran (note, wlan0 is what the TP-Link was mapped to at the time):

$ sudo udevadm test /sys/class/net/wlan0

To get the values to specify in ATTRS{...}, I used lsusb:

$ sudo lsusb
Bus 001 Device 004: ID 046d:c52b Logitech, Inc. Unifying Receiver
Bus 001 Device 009: ID 2357:010c TP-Link TL-WN722N v2
Bus 001 Device 006: ID 0424:7800 Standard Microsystems Corp.
Bus 001 Device 003: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 002: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

$ lsusb -d 2357:010c
Bus 001 Device 009: ID 2357:010c TP-Link TL-WN722N v2

$ lsusb -d 2357:010c -v
Bus 001 Device 009: ID 2357:010c TP-Link TL-WN722N v2
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x2357 TP-Link          <------- this is what we're looking for
  idProduct          0x010c TL-WN722N v2     <------- this too...
  bcdDevice            0.00
  iManufacturer           1 Realtek
  iProduct                2 802.11n NIC
  iSerial                 3 00E04C0001
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           39
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0
    bmAttributes         0xa0
      (Bus Powered)
      Remote Wakeup
    MaxPower              500mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           3
      bInterfaceClass       255 Vendor Specific Class
      bInterfaceSubClass    255 Vendor Specific Subclass
      bInterfaceProtocol    255 Vendor Specific Protocol
      iInterface              0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x02  EP 2 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x03  EP 3 OUT
        bmAttributes            2
          Transfer Type            Bulk
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0200  1x 512 bytes
        bInterval               0
Device Qualifier (for other device speed):
  bLength                10
  bDescriptorType         6
  bcdUSB               2.00
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0
  bDeviceProtocol         0
  bMaxPacketSize0        64
  bNumConfigurations      1
Device Status:     0x0002
  (Bus Powered)
  Remote Wakeup Enabled

The Arch Wiki pointed me in the general direction sort of, but finding this attribute information was… not intuitive. Sometimes I think hardware people don’t like documentation. 🤕