Revision 0:4d02779757de, committed 2016-05-06

Comitter:

skelter

Date:

Fri May 06 18:52:40 2016 +0000

Commit message:

Commit start

Changed in this revision

diff -r 000000000000 -r 4d02779757de VoltageRead.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/VoltageRead.h	Fri May 06 18:52:40 2016 +0000
@@ -0,0 +1,36 @@
+
+#include <math.h>
+
+#define VOLTAGE_SCALE_FACTOR    3.3/4096
+#define CHANNEL_OFFSET          1.72*(4096/3.3)//2048
+
+
+DigitalOut flag(p9);
+
+float get_voltage_rms(void)
+{
+  
+  int sum=0;
+  int voltage[VOLTAGE_SAMPLES];
+
+  
+  // loop takes 7.3ms
+  // with wait_us(1) loop takes 7.65ms. diff = 0.35ms
+  // with wait_us(2) loop takes 7.91ms. diff = 0,61ms
+  // with wait_us(3) loop takes 8.15ms. diff = 0,85ms
+  flag=1;
+  for(int i=0;i<VOLTAGE_SAMPLES;i++)
+  {
+    voltage[i]=(float)ReadAnalogMCP3201() - CHANNEL_OFFSET;
+    sum+=(voltage[i]*voltage[i]);
+    wait_us(36);
+  }  
+  flag=0;   
+  
+  //dump the AD samples to global variable "samples"
+  for(int i=0;i<VOLTAGE_SAMPLES;i++) samples[i]=voltage[i];
+  
+  //calculate RMS
+  return (float)sqrt((double)(((float)sum / VOLTAGE_SAMPLES)))*VOLTAGE_SCALE_FACTOR;
+      
+}
\ No newline at end of file

diff -r 000000000000 -r 4d02779757de main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Fri May 06 18:52:40 2016 +0000
@@ -0,0 +1,84 @@
+/* 
+    Read analog channel from MCP3201 with SPI interface and send it to the serial interface.
+    Matlab can be used to evaluate the sampled wave.
+*/
+
+
+#include "mbed.h"
+
+#define VOLTAGE_SAMPLES         255
+
+// for samples serial dumping 
+int samples[255];
+
+#include "mcp3201.h"
+#include "VoltageRead.h"
+
+Serial pc(USBTX, USBRX); // tx, rx
+
+int main() 
+{
+    pc.baud(115200);
+    pc.printf("Ola Sr. Matlab!");
+    
+    while(1) 
+    {  
+        float rms_value=get_voltage_rms();
+        for(int i=0;i<VOLTAGE_SAMPLES;i++) pc.printf("%i\r\n", samples[i]);
+        //end of com
+        pc.printf(" ");
+        
+        //run Matlab script again to get new sample
+        char c = pc.getc();
+    }
+}
+
+/*
+s=serial('COM6','BAUD',115200,'Terminator',' ','InputBufferSize', 8096,'OutputBufferSize',1024);
+fopen(s);
+fprintf(s,'c','async');
+x=fscanf(s);
+y=str2num(x);
+
+ADC_OFFSET=floor(1.7*(4096/3.3));
+ADC_SCALE=(2110*sqrt(2))/4096; %Valor de Tensao no pino 3.3/4096
+VOLTAGE_SAMPLES=256;
+
+t=linspace(0,inv(60)*VOLTAGE_SAMPLES/256,VOLTAGE_SAMPLES-1);
+
+figure(1);
+subplot(2,1,1)
+%stem(y.*(3.3/4096),'x.'); grid;
+stem(y+ADC_OFFSET,'.'); grid;
+title('Sampled Wave from MCP3201');
+xlabel('Sample Number [0...255]');
+ylabel('Sampled Value [0...4095)');
+
+subplot(2,1,2)
+stem(y,'.','b'); grid;
+title('Offset Adjustment to RMS calculation');
+xlabel('Sample Number [0...255]');
+ylabel('Sampled Value [-2048...2047)');
+
+figure(2);
+stairs(t,y.*(ADC_SCALE)); grid;
+title('Reconstructed wave');
+xlabel('time [s]');
+ylabel('Voltage [Volts)');
+%hold on
+%plot(y.*(ADC_SCALE),'--');
+%hold off
+
+rms=sqrt(mean((y.^2)))*ADC_SCALE;
+disp('  Valor RMS')
+disp(rms)
+
+fclose(s);
+clear s;
+% sometimes the channel remains open, use this
+% fclose(instrfind)
+*/
+
+
+    
+

diff -r 000000000000 -r 4d02779757de mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Fri May 06 18:52:40 2016 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/99a22ba036c9
\ No newline at end of file

diff -r 000000000000 -r 4d02779757de mcp3201.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mcp3201.h	Fri May 06 18:52:40 2016 +0000
@@ -0,0 +1,34 @@
+/*
+    Header for MCP3201 Analog SAR Converter with SPI interface 
+    Version: 1.0
+    Julio S.
+*/
+
+// SPI clock freq. in HZ
+// Limits from MCP3201 datasheet are:
+// 1500000Hz when vdd=5V
+// 800000Hz when vdd=2.7V
+// 1MHz should work.
+#define MCP3201_CLK_FREQ    1000000
+
+// MCP3201 SPI channel pinout
+// p5 not wired, there are no commands to send for MCP3201 device
+SPI MCP3201(p5,p6,p7);
+// take control from CS pin to avoid transition changes between write commands
+DigitalOut cs(p8); 
+
+
+// Read the analog value from MCP3201.
+// return 12bit interger (0...4095)
+int ReadAnalogMCP3201(void)
+{
+ MCP3201.frequency(MCP3201_CLK_FREQ);
+ 
+ cs=0;
+ int high_byte = MCP3201.write(0x00);
+ int low_byte = MCP3201.write(0x00);
+ cs=1;
+ int conv_result = ((high_byte & 0x1f) << 7) | ((low_byte >> 1) & 0x7f);  
+
+ return conv_result;
+}
\ No newline at end of file