Retry firmware query if payload seems implausibly small

[nigels-com]

In relation to Issue #9

Bus 003 Dev 006 413d:2107 V3.3 Error: Unknown firmware V3.3: b'800108984e200000'

I had some success with TEMPer1F 413d:2107 that was alternating between TEMPerX_V3.3 and V3.3 as the firmware version.

This change tries ten times to read the firmware while 0 < length < 9

See the issue for further diagnostics.

[nigels-com]

Showing the retry in action...

$ sudo cat /sys/kernel/debug/usb/usbmon/3u | grep ':3:006:'
ffff8bbec3e593c0 3943174349 S Ii:3:006:2 -115:8 8 <
ffff8bc25f5cccc0 3943232132 S Io:3:006:2 -115:8 8 = 0186ff01 00000000
ffff8bc25f5cccc0 3943236425 C Io:3:006:2 0:8 8 >
ffff8bbec3e593c0 3943312462 C Ii:3:006:2 0:8 8 = 56332e33 20202020
ffff8bbec3e593c0 3943312475 S Ii:3:006:2 -115:8 8 <
ffff8bc26564e000 3943412672 S Io:3:006:2 -115:8 8 = 0186ff01 00000000
ffff8bc26564e000 3943420471 C Io:3:006:2 0:8 8 >
ffff8bbec3e593c0 3943424434 C Ii:3:006:2 0:8 8 = 54454d50 6572585f
ffff8bbec3e593c0 3943424445 S Ii:3:006:2 -115:8 8 <
ffff8bbec3e593c0 3943496443 C Ii:3:006:2 0:8 8 = 56332e33 20202020
ffff8bbec3e593c0 3943496454 S Ii:3:006:2 -115:8 8 <
ffff8bc26564e0c0 3943596663 S Io:3:006:2 -115:8 8 = 01803301 00000000
ffff8bc26564e0c0 3943604451 C Io:3:006:2 0:8 8 >
ffff8bbec3e593c0 3943680457 C Ii:3:006:2 0:8 8 = 800108dc 4e200000
ffff8bbec3e593c0 3943680466 S Ii:3:006:2 -115:8 8 <
ffff8bbec3e593c0 3943781525 C Ii:3:006:2 -2:8 0
ffff8bbec3e593c0 3944598482 S Ii:3:006:2 -115:8 8 <

[nigels-com]

In relation to discussion over on Issue #9

Linux PC

$ while true; do sudo ./temper.py; sleep 1; done
Bus 003 Dev 011 413d:2107 TEMPerX_V3.3 24.1C 75.3F - - - -
Bus 003 Dev 011 413d:2107 TEMPerX_V3.3 24.2C 75.5F - - - -
Bus 003 Dev 011 413d:2107 TEMPerX_V3.3 24.1C 75.4F - - - -
Bus 003 Dev 011 413d:2107 TEMPerX_V3.3 24.1C 75.4F - - - -
Bus 003 Dev 011 413d:2107 TEMPerX_V3.3 24.1C 75.4F - - - -
Bus 003 Dev 011 413d:2107 TEMPerX_V3.3 24.1C 75.4F - - - -
...

[bucklevision]

Made both of these changes and updated the timeout from 0.2 to 0.5 and still get failures every other read when running
while true; do sudo ./temper2.py; sleep 5; done
on an RPi 3 B+

Just investigating, the regularity of it made me call hardware into question, checking dmesg it shows brownout on each successful read, subsequently returning rubbish. Will confirm with new PSU.

__ Update:
PSU swapped for a high current one, no improvement - power drop out doesn't happen but still get errors.

Output modified as I don't need all the bumf, but....
--@--:/home/pi# ./temper2.py
21.5 2020-01-21 21:01:39
--@--:/home/pi# ./temper2.py
21.5 2020-01-21 21:01:41
--@--:/home/pi# ./temper2.py
Traceback (most recent call last):
File "./temper2.py", line 434, in
sys.exit(temper.main())
File "./temper2.py", line 427, in main
results = self.read(args.verbose)
File "./temper2.py", line 345, in read
results.append({ **info, **usbread.read() })
File "./temper2.py", line 272, in read
return self._read_hidraw(self.device)
File "./temper2.py", line 180, in _read_hidraw
firmware = self._read_hidraw_firmware(fd, self.verbose)
File "./temper2.py", line 159, in _read_hidraw_firmware
raise RuntimeError('Cannot read device firmware identifier')
RuntimeError: Cannot read device firmware identifier

[nigels-com]

@bucklevision Could you mention the specific Temper USB model and the output of lsusb? Thanks.

[bucklevision]

Sure, sorry, not very helpful!

It seems to happen with successive calls within 2ish seconds. Give it 5 and most of the time it's OK.

lsusb:
Bus 001 Device 005: ID 0c45:7401 Microdia TEMPer Temperature Sensor
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. SMSC9512/9514 Fast Ethernet Adapter
Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp. SMC9514 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

output of /sys/kernel/debug/usb/devices
T: Bus=01 Lev=02 Prnt=02 Port=02 Cnt=02 Dev#= 5 Spd=1.5 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1
P: Vendor=0c45 ProdID=7401 Rev= 0.01
S: Manufacturer=RDing
S: Product=TEMPerV1.4
C:* #Ifs= 2 Cfg#= 1 Atr=a0 MxPwr=100mA
I:* If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=01 Driver=usbhid
E: Ad=81(I) Atr=03(Int.) MxPS= 8 Ivl=10ms
I:* If#= 1 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=usbhid
E: Ad=82(I) Atr=03(Int.) MxPS= 8 Ivl=10ms

It's one of these:
https://pcsensor.com/usb-thermometers/gold-temper.html

However it was purchased from Amazon.

[nigels-com]

@bucklevision I filed Issue #20 to follow up for TEMPerV1.4 and RPi3 B+. There is a workaround, so far.