Connect2Pi - Complaint!

  
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Connect2Pi - Complaint!

Postby WirelessMike » Mon Jul 29, 2013 2:58 pm

This complaint was emailed to our Technical Department and an edited version is copied here as it contains useful information:

I am very disappointed about the way you advertise the ERA-Connect2-PI modules. You mention that data rates of 115kBaud were possible, but as it turns out that is only the case for the host side! You should be aware that this information is completely useless, as the point is to transmit data over the wireless link, so only the “over air” rate of 38400Baud is obtainable.

Furthermore, the latencies are enormous (in the order of 20ms, depending on the data rate), so your remark on the “seamless” data transfer has to be interpreted with caution. Quote:

"Host devices can send and receive (half duplex) up to 180 Bytes of data per packet that will be seamlessly delivered and presented to other hosts within range. There is no need for any complicated ‘bit balancing’ or elaborate coding schemes. Easy: Data In and Data Out !

I have just wasted my money and two hours of testing !

Unhappy Customer
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WirelessMike
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Re: Connect2Pi - Rubbish !

Postby WirelessMike » Mon Jul 29, 2013 3:01 pm

Dear Sir,

We are so sorry that you you feel our datasheet has mislead you - please let me explain:

The PI Dongle is fitted with an eRA900TRS RF Module which is the most configurable low power radio module on the market today.These modules are designed for use on low power ISM bands and achieve long distance/range by utilising a relatively low receiver bandwidth to improve selectivity, sensitivity, and susceptibility to interference. Referring to the actual ‘effective’ data rate, in the default bandwidth this is 9600 bps.

Regarding your latency comment, this is perfectly normal.

The radio, uploads and packetises the host's transmit serial data, adding a preamble, package information and CRC (Cyclic Redundancy Check) bytes before transmitting it 'over air', and will do this for any packet up to a maximum of 180 bytes. (Data encryption is also optionally available).

The receiver in turn, descrambles the over air data and delivers it to the host at the BAUD rate set on the module. All these consecutive 'serial' processes take time. This is therefore 'seamless' as, 'what goes in is what comes out !'

The module is capable of operating down to 12.5KHz channel spacing (But this will slow the data rate down to 1200bps) and can be as high as 100KHz bandwidth. The RS232 BAUD rates are adjustable for convenience or to improve the overall upload/download times if required.

Your quote of 20mS is relative to the data rate selected and the size of packet, it could be shorter or even much longer. You will therefore have to consider these delays in your design.

For your application, that requires continuous high data throughput, this device may not the right choice !
Please contact our distributor who will be pleased to credit your account upon return of the dongles.
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