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Edited by olauah at 2017-8-4 20:46
My 2 week experience with the 2G-IOT, using mostly the ubuntu image, but also tested Debian and Armbian, is that:
- It is highly sensitive to the power supply and even if it boots, some things may fail later due to "unsuited" supply. Tested with 2A, 3A chargers (all original from Apple, Huawei and Blitzwolf), as well as with 3A DC-DC step down modules, and a HP lab power supply. A small resistance in the cable (e.g 0.5-1ohm) is enough to cause trouble, even if the supply provides 5.000V stable. It also not just a matter of max Amps available but also the noise produced by the supply. A capacitor in the DC line may help, however I only saw some changes with a 5000uf capacitor, which is not practical.
- Using an lab power supply and a oscilloscope I determined that while idle, the power consumption is ~60% of the time around 90mA, then it increases to ~250mA for the remaining 40% of the time, and the cycle restarts. During this time, it will repeatedly demand almost 2A during ~50ns. (do not have the traces here, and the values are from memory, but I can provide them later). This is not a friendly behaviour for any power supply and I assume it could be producing some of interference.
- GSM Modem works ok if the power supply is reasonable. The first symptom of a bad power supply seems to be failure to detect the SIM card insertion, resulting in CME ERROR: 10.
- Wifi is terribly unstable and almost not usable for a continuous session. It seems to be the first component to fail with a "less good" power supply. There are many packet losses and high jitter (crda installed, power save off).
Also, the behavior is different depending on the traffic direction:
Tested in a wifi network in channel 1, with no other network in the same channel and no traffic in the wireless network, using WPA and a Huawei 802.11ac router.
Ping from 2G-IOT (102.168.1.20) to another wifi host (192.168.1.67):
PING 192.168.1.67 (192.168.1.67) 56(84) bytes of data.
64 bytes from 192.168.1.67: icmp_seq=1 ttl=64 time=3.29 ms
64 bytes from 192.168.1.67: icmp_seq=2 ttl=64 time=67.3 ms
64 bytes from 192.168.1.67: icmp_seq=3 ttl=64 time=47.7 ms
64 bytes from 192.168.1.67: icmp_seq=4 ttl=64 time=42.6 ms
64 bytes from 192.168.1.67: icmp_seq=5 ttl=64 time=19.9 ms
64 bytes from 192.168.1.67: icmp_seq=6 ttl=64 time=47.9 ms
64 bytes from 192.168.1.67: icmp_seq=7 ttl=64 time=43.2 ms
64 bytes from 192.168.1.67: icmp_seq=8 ttl=64 time=22.3 ms
64 bytes from 192.168.1.67: icmp_seq=9 ttl=64 time=39.9 ms
64 bytes from 192.168.1.67: icmp_seq=10 ttl=64 time=35.4 ms
--- 192.168.1.67 ping statistics ---
12 packets transmitted, 10 received, 16% packet loss, time 11048ms
rtt min/avg/max/mdev = 3.293/37.005/67.381/16.971 ms
simultaneous ping from the wifi host (192.168.1.67) to the 2G-IOT (192.168.1.20)
PING 192.168.1.20 (192.168.1.20): 56 data bytes
64 bytes from 192.168.1.20: icmp_seq=0 ttl=64 time=552.454 ms
64 bytes from 192.168.1.20: icmp_seq=1 ttl=64 time=82.929 ms
64 bytes from 192.168.1.20: icmp_seq=2 ttl=64 time=204.815 ms
64 bytes from 192.168.1.20: icmp_seq=3 ttl=64 time=559.674 ms
64 bytes from 192.168.1.20: icmp_seq=4 ttl=64 time=80.399 ms
64 bytes from 192.168.1.20: icmp_seq=5 ttl=64 time=307.805 ms
64 bytes from 192.168.1.20: icmp_seq=6 ttl=64 time=564.616 ms
64 bytes from 192.168.1.20: icmp_seq=7 ttl=64 time=91.208 ms
64 bytes from 192.168.1.20: icmp_seq=8 ttl=64 time=367.757 ms
64 bytes from 192.168.1.20: icmp_seq=9 ttl=64 time=571.671 ms
64 bytes from 192.168.1.20: icmp_seq=10 ttl=64 time=100.303 ms
64 bytes from 192.168.1.20: icmp_seq=11 ttl=64 time=372.485 ms
--- 192.168.1.20 ping statistics ---
13 packets transmitted, 12 packets received, 7.7% packet loss
round-trip min/avg/max/stddev = 80.399/321.343/571.671/197.338 ms
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