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imp003 RF Certification Guide

Performing RF Certification Testing on Your imp003 Design

The imp003 (Murata Module LBWA1ZV1CD) does not incorporate a 2.4GHz antenna. Consequently, customers must implement either an Electric Imp-recommended antenna option, or an antenna design of their own. Choosing an Electric Imp-recommended solution significantly reduces the degree of testing the customer must undertake to achieve full FCC/IC certification for their complete product.

Electric Imp recommends that customers choose either our own PIFA antenna or our selected chip antenna. Both of these imp003-and-antenna options have received FCC and IC modular certification. There is more information about FCC/IC modular certification here.

The Electric Imp RF Test Kit

RF certification testing is not performed with standard production imp003 modules. Instead, testing is performed with an imp003 pre-loaded with RF test software. The RF test software allows the radio to be configured with a set of simple serial commands, sent over an FTDI USB-to-Serial cable.

Prepare the Test Hardware

RF testing also requires a Windows PC on which to run a command-line tool, WL.EXE, to send commands to the RF test imp003 via USB and serial. We recommend that all customers who need to run RF testing ensure that uartQR is able to be used for RF testing, as this is the only supported UART; if the pins are used for other purposes in the product, then ensure that the lines can easily be disconnected (for example, via 0R resistors) to prevent contention when in test mode.

The RF test imp003 — the Unit Under Test (UUT) — should then be soldered to your product PCBA and the FTDI cable connected as follows.

  1. Solder the FTDI cable Black wire to GND
  2. Solder the FTDI cable Yellow wire (RXD) to imp003 pinQ
  3. Solder the FTDI cable Orange wire (TXD) to imp003 pinR
  4. Leave the FTDI cable’s Brown (CTS_L), Red (VCC) and Green (RTS_L) wires disconnected

The RF Test Software

  1. Download FTDI’s virtual COM port driver and install it on the test PC.
  2. File a Support Ticket to request the WL.EXE test software and Electric Imp batch files.
  3. You will receive a link to the software, which you should download on the test PC and unzip.

RF Testing with WL.EXE

First, plug in the FTDI cable, then open Windows’ Device Manager and note the COM port number of the FTDI cable. This will be passed to the WL.EXE tool via the <comport> parameter.

Open a command prompt and navigate to the directory containing WL.EXE tool. Three tests are available, each performed by running the appropriate batch file at the command line. The tests are as follows:

2g_rx <comport> <channel>

This will set the UUT into RX mode on the specified channel. This is used to check for receiver leakage.

2g_cw_output <comport> <channel>

This sets the UUT to transmit a carrier wave at 15.0dBm. This is used to check frequency accuracy.

2g_tx <comport> <country> <channel> <modulation> <bitrate>

This sets the UUT to transmit high duty-cycle packets at the appropriate modulation, channel and power settings for the specified country. This is used to check modulation quality, channel occupancy, spurious emissions, etc.

The parameters for each of these tests are as follows:

  • <comport> is the COM port number that the UUT is connected to.
    For example, if it is on COM7, this should be 7.
  • <country> is the regulatory domain.
    US = USA/Canada, EU = Europe/rest of world. 802.11b power is lower for EU than US.
  • <channel> is the channel to be used. Valid ranges are: 1-11 for US, 1-13 for EU.
  • <modulation> is the required modulation (802.11 b, g or n).
  • <bitrate> is the required bitrate or MCS level:
    • For 802.11b, acceptable values are 1, 2, 5.5 or 11.
    • For 802.11g, acceptable values are 6, 9, 12, 18, 24, 36, 48, 54.
    • For 802.11n, this is the MCS level 0 (6.5Mb/s) to 7 (65Mb/s).

Each test script will check that the first command issued does not return an error. If an error is returned, the script assumes that the UUT is not responding — please check that you have the correct COM port number.

WL.EXE automatically sets the correct baud rate for the UUT.