I have a Pi Zero W running software that constantly retrieves internet information (there is no reason for the WiFi to "sleep" although I think I've already turned off all the power-save stuff). Every few days, the WiFi connection just STOPS. My router security is "WPA2 Personal" it's an Apple router and I don't have many more options.
I was still able to access the Pi via USB/RNDIS/Ethernet Gadget mode so I could at least retrieve some information while it's off-WiFi:
ifconfig - WHILE WIFI IS DOWN
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:371953 errors:0 dropped:0 overruns:0 frame:0
TX packets:371953 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1
RX bytes:117420716 (111.9 MiB) TX bytes:117420716 (111.9 MiB)
usb0 Link encap:Ethernet HWaddr 12:61:9d:58:71:e7
inet addr:192.168.2.20 Bcast:192.168.2.255 Mask:255.255.255.0
inet6 addr: fe80::b4f1:b5d:5f46:2804/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:30346 errors:0 dropped:0 overruns:0 frame:0
TX packets:25046 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:21326729 (20.3 MiB) TX bytes:11436261 (10.9 MiB)
wlan0 Link encap:Ethernet HWaddr b8:27:eb:fd:8e:43
inet6 addr: fe80::55e6:6635:aa91:21c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2677376 errors:0 dropped:251 overruns:0 frame:0
TX packets:1905430 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1769016413 (1.6 GiB) TX bytes:335795383 (320.2 MiB)
ip addr show - WHILE WIFI IS DOWN
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: usb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 12:61:9d:58:71:e7 brd ff:ff:ff:ff:ff:ff
inet 192.168.2.20/24 brd 192.168.2.255 scope global usb0
valid_lft forever preferred_lft forever
inet6 fe80::b4f1:b5d:5f46:2804/64 scope link
valid_lft forever preferred_lft forever
3: wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether b8:27:eb:fd:8e:43 brd ff:ff:ff:ff:ff:ff
inet6 fe80::ba27:ebff:fefd:8e43/64 scope link
valid_lft forever preferred_lft forever
iwconfig - WHILE WIFI IS DOWN
usb0 no wireless extensions.
wlan0 IEEE 802.11 ESSID:off/any
Mode:Managed Access Point: Not-Associated Tx-Power=31 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Power Management:off
lo no wireless extensions.
ifconfig - WHEN WIFI IS BACK UP
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:371977 errors:0 dropped:0 overruns:0 frame:0
TX packets:371977 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1
RX bytes:117502451 (112.0 MiB) TX bytes:117502451 (112.0 MiB)
usb0 Link encap:Ethernet HWaddr 12:61:9d:58:71:e7
inet addr:192.168.2.20 Bcast:192.168.2.255 Mask:255.255.255.0
inet6 addr: fe80::b4f1:b5d:5f46:2804/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:30586 errors:0 dropped:0 overruns:0 frame:0
TX packets:25274 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:21361874 (20.3 MiB) TX bytes:11479732 (10.9 MiB)
wlan0 Link encap:Ethernet HWaddr b8:27:eb:fd:8e:43
inet addr:10.0.1.169 Bcast:10.0.1.255 Mask:255.255.255.0
inet6 addr: fe80::55e6:6635:aa91:21c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:2677377 errors:0 dropped:251 overruns:0 frame:0
TX packets:1905461 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1769016749 (1.6 GiB) TX bytes:335802150 (320.2 MiB)
ip addr show - WHEN WIFI IS BACK UP
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: usb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether a6:30:3f:a5:9e:a3 brd ff:ff:ff:ff:ff:ff
inet 192.168.2.21/24 brd 192.168.2.255 scope global usb0
valid_lft forever preferred_lft forever
inet6 fe80::a430:3fff:fea5:9ea3/64 scope link
valid_lft forever preferred_lft forever
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether b8:27:eb:fd:8e:43 brd ff:ff:ff:ff:ff:ff
inet 10.0.1.169/24 brd 10.0.1.255 scope global wlan0
valid_lft forever preferred_lft forever
inet6 fe80::ba27:ebff:fefd:8e43/64 scope link
valid_lft forever preferred_lft forever
iwconfig - WHEN WIFI IS BACK UP
usb0 no wireless extensions.
wlan0 IEEE 802.11 ESSID:"outerspace"
Mode:Managed Frequency:2.437 GHz Access Point: 3C:15:C2:F2:61:18
Bit Rate=57.7 Mb/s Tx-Power=31 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Power Management:off
Link Quality=70/70 Signal level=-17 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:1 Invalid misc:0 Missed beacon:0
lo no wireless extensions.
/etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'
# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d
auto wlan0
auto lo usb0
iface lo inet loopback
iface eth0 inet manual
allow-hotplug wlan0
iface wlan0 inet manual
wireless-power off
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
post-up iw wlan0 set power_save off
allow-hotplug wlan1
iface wlan1 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
allow-hotplug usb0
iface usb0 inet manual
/var/log/messages
and what does the "software that retreive..." log say? – MatsK Sep 14 '17 at 02:40