Problems with CF-RU5400 RFID Reader from Shenzhen Chafon Technology Co.

Post date: Jun 13, 2014 6:24:28 PM

I recently received emails from the Shenzhen Chafon Technology Company about their passive RFID reader, the CF-RU5400.

I later learned that the CF-RU5400 is available for about 1/2 the cost of an Impinj reader. This sounded interesting.

Impressed with the price, I reviewed the SDK (Software Development Kit) to see if it would be easy to build an interface to it.

The CF-RU5400 does not support the industry-standard LLRP (Low-Level Reader Protocol), so the CrossMgr utilities will not talk to it. It has a proprietary, binary message protocol. I also could not find published performance characteristics for it, such as tags/second read time (most readers quote 300-400 reads/second).

In the end, none of this matters.

The docs show that the CF-RU5400 only supports time resolution to seconds (not milliseconds, not microseconds).

This makes it unsuitable for bike racing, where time trials and close bunch finishes are the norm.

This limitation is in the communication protocol (see below), and there do not appear any options to change it.

By contrast, the industry-standard LLRP protocol defines times as 64-bit numbers representing microseconds (millionths of a second) since Jan 1st, 1970.

In practice an LLRP reader (eg. Impinj 440) may not be capable of resolving at this resolution due to clock speed, etc.

That's OK - if it only resolves to milliseconds, that's good enough.

The CF-RU5400 communication protocol returns date/time packed into a 32-bit number with no fractions of a second.

If I misunderstood this, please let me know!

This is the excerpt from page 36 of the UHF RFID Fixed Reader CF-RU5400 User's Manual V1.6:

DiscTime: 4 bytes. It specifies the time stamp when the tag is firstly detected.

Year: 6bits. It ranges from 0 to 63 for year 2000 to 2063.

Month: 4bits. It ranges from 1 to 12 for Jan. to Dec.

Date: 5bits. It ranges from 1 to 31 for day 1 to day 31.

Hour: 5bits. It ranges from 0 to 23.

Minute: 6bits. It ranges from 0 to 59.

Second: 6bits. It ranges from 0 to 59.