4 years, 9 months ago.

Error in code for wifly

Hey I made the following code but I get an Error: Identifier "ws" is undefined in "main.cpp", Line: 73, Col: 2. The idea for the code is to receive a ECG input which is filtered and then sent to the mbed website. I cant seem to see where I went wrong. Would appreciate if someone cold point it out.

#include "mbed.h"
#include "WiflyInterface.h"
#include "Websocket.h"

AnalogIn Ain(p20);
#define NCoef 4                 // NCoef is equal to 4

/* wifly object where:            mbed              - RN-XV
*     - p9 and p10 are for the serial communication - p3, p2
*     - p11 is for the reset pin                    - p5
*     - p26 is for the connection status            - p15
*     - "mbed" is the ssid of the network
*     - "password" is the password
*     - WPA is the security
WiflyInterface wifly(p9, p10, p11, p26, "mbed", "1234567890", WPA);

Ticker s2khz_tick;
void s2khz_task(void);          // Declare function

float iir(float NewSample) 
float ACoef[NCoef+1] = {
    0.98440741971685686000,         // coefficients

float BCoef[NCoef+1] = {
    1.00000000000000000000,         // coefficients

static float y[NCoef+1]; //output samples
static float x[NCoef+1]; //input samples
int n;

//shift the old samples
for(n=NCoef; n>0; n--) {
   x[n] = x[n-1];
   y[n] = y[n-1];

//Calculate the new output
x[0] = NewSample;
y[0] = ACoef[0] * x[0];
for(n=1; n<=NCoef; n++)
    y[0] += ACoef[n] * x[n] - BCoef[n] * y[n];

return y[0];            // return new filtered data


void s2khz_task(void)
float data_in, data_out, ecg;        // Declaring float variables    
char package[30];
data_out=iir(data_in);      // Retreiving new filtered data 
sprintf (package, "{\"ecg\":%f}", ecg);

int main() 
    wifly.init();               // use DHCP
    while (!wifly.connect());   // join the network
    Websocket ws("ws://");
    s2khz_tick.attach_us(&s2khz_task,500);      // uses function every 500ms

Please use proper headline name for the feature, the error is in your code (=user) , not in the wifly library. Thanks !

posted by Martin Kojtal 30 May 2014
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1 Answer

4 years, 9 months ago.

You declare ws within the scope of main in line 80, but you try to use ws inside the s2khz_task, where it is unknown. Try declaring it at or before line 61.

Thanks Wim. Ye stupid mistake. I moved it to line 7 and it compiles, however now I get lights of death so I must have a runtime error. I had two seperate programs, one for filtering and one for wifly connection and both work, so here I am trying to combine the two, but I am ust not seeing the problem, anyone have any ideas?

edit: After just trying the old code with the same edit, i.e. moving the ws to line 7, I got the same problem. Putting the ws on line 62 solved the problem, but I dont understand why it makes a difference if its on line 61 or line 7.

posted by Johann Hur 30 May 2014

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