PW Data Modes Fig 6 Corrected

I made a mistake in the diagram pin numbering showing the serial connection to the Olimex ESP8266-DEV board. The ground should connect to pin 2 as shown using the numbering in the revised Fig.6.

Apologies for the error,

Mike

Copy and paste the code below into your Arduino IDE:
 --------------------------------------------------------------------------------------------------------------------------
 /*
 This sketch uses the Adafruit i2c/SPI LCD backpack
 and shares some code from Adafruit
 ( http://www.ladyada.net/products/i2cspilcdbackpack/index.html )

Sketch produced by Mike Richards (G4WNC) for publication in the August issue
 of Practical Wireless magazine in the UK
 www.g4wnc.com

The LCD Backpack connections:
 * 5V to Arduino 5V pin
 * GND to Arduino GND pin
 * CLK to Analog #5
 * DAT to Analog #4

* The AD8307 voltage output connects to the Arduino A0 pin

*/

// include the library code:
 #include "Wire.h"
 #include "LiquidCrystal.h"

// Initialise the variables
 int value = 0; // Used to store the raw reading from the ADC
 float vout = 0.000; // Holds the true value of the ADC output voltage
 float powerdB = 0.00; // Calculated power in dBm
 float pWatts = 0.00; // Calculated power in watts
 float slope = 40; // Slope of the AD8307 log output (Default = 40)
 float intercept = 44.0; // 0V intercept point (Default = 44)
 float refVolts = 2.5; // Measured value of the 2.5V external reference

// Connect to the LCD via i2c, default address #0 (A0-A2 not jumpered)
 LiquidCrystal lcd(0);

void setup() {
 // Start by setting-up the pin configurations
 analogReference(EXTERNAL); // Set the Arduino to use an external reference for the ADC
 pinMode(4, OUTPUT); // Digital pin 4 is used to supply power to the voltage reference
 digitalWrite(4, HIGH); // Make sure pin 4 is high
 pinMode(A0, INPUT); // Enable the first (A0) input to the ADC
 // set up the LCD's number of rows and columns:
 lcd.begin(20, 4); // Set 4 lines of 20 characters
 // Print a message to the LCD.
 lcd.setCursor(0,0); // set the cursor to the top left, line 0 column 0
 lcd.print("Arduino Power Meter"); // Message on the top line of the display
 lcd.setBacklight(HIGH); // Turn the backlight on to make the display visible
 //Now print the measurement labels
 lcd.setCursor(0,1); // move the cursor to the first position on the 2nd line
 lcd.print("AD8307 Volts: "); // print the label
 lcd.setCursor(0, 2); // Move the cursor to the start of the 3rd line
 lcd.print("Power (dBm): "); // Print the label
 lcd.setCursor(0, 3); // Position the cursor
 lcd.print("Power (Watts):"); // Print the label
 }

void loop() {

value = analogRead(0); //read the ADC and store the result in value
 vout = (value*refVolts)/1023; // Convert the ADC result to volts in vout
 powerdB = (slope*vout)-intercept; // convert the voltage to dBm in 50 ohms
 pWatts = pow(10.0,(powerdB -30)/10.0); // convert dBm to watts
 lcd.setCursor(13, 1); //Move the cursor to the 13th position
 lcd.print(vout,3); // Display the AD8307 voltage
 lcd.setCursor(13, 2); // Position the cursor
 lcd.print(" "); // Print spaces to clear the last result
 lcd.setCursor(13, 2); // Position the cursor
 lcd.print(powerdB,1);// Display the power in dBm
 lcd.setCursor(15,3); // Position the cursor
 lcd.print(" "); // Print spaces to clear the last result
 lcd.setCursor(15,3); //Position the cursor
 lcd.print(pWatts,1);// Display the power in watts
 }

The one weak point is the programming instructions that don’t really cover the USB connected development boards but assume you have a PSoC programmer. The solution to is use the following excellent Wiki that provides step-by-step instructions on USB bootloader programming: Bootloader Wiki.

Another supplier worth watching is Anarduino as they supply lots of similar boards but are currently revising their range.

I’ve got a few boards on order so watch out for my columns in PW and Radio User for more information.

This standalone, free, software package helps you set up all the peripherals in a visual format. This includes all the communication port options as well as the clock chain. The visual clock programming is a real breakthrough as the software provides a simple block diagram of all the clocks showing how they interact. Once you’ve set-up the interfaces and clocks, the Cube MX software generates C code that you can use as the foundation for your project. This is a real boon as not only does it save time but it ensures that you have optimised setup code.

The STM32Cube MX sofware can be downloaded from here.

The new Nucleo boards are fantastic value priced at just under £8 each from Farnell. The four boards in the initial launch cover M0, M3 and M4 Cortex processors with an assortment of ADCs, DACs and communications interfaces.

Up until recently, development kits for this technology have been too pricey for the enthusiasts market but that is changing rapidly. The latest to come to my attention is the Cypress CY8CKIT-042 PSoc Pioneer Kit. This has everything you need to get started including an on-board programmer, USB lead and some patch wires. The development software is completely free and downloadable from the Cypress site. One of the great things about this system is the PSoc 4 Creator software that allows you to create and  program your dedicated applications by simply drawing the circuit diagram! The kit also has Arduino compatible pin layout and sockets for Digilent Pmod accessories so it’s easy to expand the board.

At the time of writing the kit was available from Farnell for about £17 which is a real bargain. Here’s a link for more information: http://uk.farnell.com/cypress-psoc-4-pioneer-kit

Development with this board has been made easy thanks to the provision of free example software, development IDE and the STemWin professional graphical library.

The package cost just under £17 which is remarkable value. You can order yours from Farnell using this link.

I’ve bought one of the Papilio One FPGA boards with a 250k gate Spartan 3E chip. In addition to the obvious FPGA chip, the board comes with all the essential voltage regulators, a clock source and its own JTAG programmer. There are two expansion wings for all the ins and outs and a USB port for the programmer. With the Palipio One board selling at just $38 (~£23) it’s great value. If you want to see more, take a look at the Learning site where you’ll find lots more detail along with examples.

I’ve also discovered an excellent CPLD development board that’s produced by Seeed Studio. This contains the same Xilinx chip as the Guzunty Pi but programming needs to be done via a JTAG lead. The board costs just $15 and postage was reasonable. There are several routes to get the necessary JTAG cable but the cheapest options are to either get a Xilinx clone cable from eBay or get the Digilent JTAG programming cable from Farnell. If you prefer to get your CPLD development board from the UK then Farnell hold the Digilent C-Mod board at £15.31.

To make your own CPLD cores you will need development software and the best option for the Xilinx chips is their free ISE WebKit.

Look out for my next Data Modes column in PW for more details.