FTBMeter - free sample software for a USB-connected power meter

FTBMeter is free sample software that demonstrates how to use the FTDI based DLP2232M-G module from DLP Design to talk to an SPI protocol device. In this implementation the program talks to a Maxim MAX187 12 bit ADC which reads the DC output level of an Analog Devices AD8307 Logarithmic Amplifier - i.e. we have a PC-linked RF power meter. 

The program displays the reading in dBm and also continuously updates a registry entry so that other software can easily acquire the information. Calibration requires a signal source of 0dBm and -40dBm. There are three ranges that can be used for calibration which are refered to as HF, VHF and UHF - the actual frequencies these relate to are up to you.

These links to the data sheets from the manufacturers web sites were current in July 2006:

   DLP2232M-G ready built USB module that can plug into a 40-pin IC socket

   MAX187 12 bit Analog Digital Converter

   AD8307 DC-500MHz 92dB Logarithmic Amplifier

The FTDI web site is a mine of information about their products and how to use them. Drivers, programming guides and source code examples in a number of programming languages are available. FTBMeter in both source and executable format can be downloaded from their Visual Basic code examples page.

FTBMeter uses the FTDI D2XX driver and DLLs to talk to the USB module. The driver/DLL version that has been tested is the Combined Driver Model V2.00.00. It is important to read the relevant installation guide for the drivers that apply to your operating system.

The updated prototype with a second BNC input for providing a pulse from the antenna rotator every degree of rotation. This pulse is used to trigger a reading of the signal strength enabling accurate readings at each of 360 degrees. The DLP2232M-G is on the left. One channel reads the ADC and the other channel detects the trigger pulse. Provision has been made for external power as well as the internal 9V battery. The brass lid of the RF sense board has been removed for the photograph.

The sample software:

An extended more accurate version of this sample software called FTBMeterV2 has been developed primarily for use in conjunction with PolarPlot. Anyone with an interest in this application is invited to email me direct. The Download page includes a link to the executable for FTBMeterV2 in the PolarPlot section.