2.3.6.2.1. Read analog voltage on a slow analog input

2.3.6.2.1.1. Description

This example shows how to measure the analog voltage of slow analog inputs on the Red Pitaya extension connector. The analog inputs on the Red Pitaya are rated from 0 to 3.3 Volts.

2.3.6.2.1.2. Required hardware

• Red Pitaya device

• R1 10k potentiometer

Wiring example for STEMlab 125-14 & STEMlab 125-10:

2.3.6.2.1.3. Circuit

2.3.6.2.1.4. SCPI Code Examples

2.3.6.2.1.4.1. Code - MATLAB®

The code is written in MATLAB. In the code, we use SCPI commands and TCP client communication. Copy the code from below into the MATLAB editor, save the project, and hit the “Run” button.

%% Define Red Pitaya as TCP client object

IP = '192.168.178.108';           % Input IP of your Red Pitaya...
port = 5000;
RP = tcpclient(IP, port);

%% Open connection with your Red Pitaya

RP.ByteOrder = "big-endian";
configureTerminator(RP,"CR/LF");

volts0 = str2double(writeread(RP,'ANALOG:PIN? AIN0'));
volts1 = str2double(writeread(RP,'ANALOG:PIN? AIN1'));
volts2 = str2double(writeread(RP,'ANALOG:PIN? AIN2'));
volts3 = str2double(writeread(RP,'ANALOG:PIN? AIN3'));

%% Close connection with Red Pitaya

clear RP;

2.3.6.2.1.4.2. Code - Python

#!/usr/bin/env python3

import sys
import redpitaya_scpi as scpi

IP = 'rp-f066c8.local'

rp_s = scpi.scpi(IP)

for i in range(4):
    rp_s.tx_txt('ANALOG:PIN? AIN' + str(i))
    value = float(rp_s.rx_txt())
    print ("Measured voltage on AI["+str(i)+"] = "+str(value)+"V")

rp_s.close()

Note

The Python functions are accessible with the latest version of the redpitaya_scpi.py document available on our GitHub. The functions represent a quality-of-life improvement as they combine the SCPI commands in an optimal order and also check for improper user inputs. The code should function at approximately the same speed without them.

For further information on functions please consult the redpitaya_scpi.py code.

2.3.6.2.1.4.3. Code - Scilab

How to set sockets is described in the Blink example.

clc

// Load SOCKET Toolbox
exec(SCI+'contribsocket_toolbox_2.0.1loader.sce');
SOCKET_init();


// Define Red Pitaya as TCP/IP object

IP= '192.168.178.56';            // Input IP of your Red Pitaya...
port = 5000;                     // If you are using WiFi then IP is:
tcpipObj='RedPitaya';            // 192.168.128.1

// Open connection with your Red Pitaya

SOCKET_open(tcpipObj,IP,port);

// Red value on analog input 3

volts=strtod(SOCKET_query(tcpipObj,'ANALOG:PIN? AIN3'));
disp(volts)

// Define value p from 0 - 100 //
p = volts *(100/3.3) ;   // Set value of p in respect to readed voltage

if p >=(100/7)
    SOCKET_write(tcpipObj,'DIG:PIN LED1,1')
else
    SOCKET_write(tcpipObj,'DIG:PIN LED1,0')
end

if p >=(100/7)*2
    SOCKET_write(tcpipObj,'DIG:PIN LED2,1')
else
    SOCKET_write(tcpipObj,'DIG:PIN LED2,0')
end

if p >=(100/7)*3
    SOCKET_write(tcpipObj,'DIG:PIN LED3,1')
else
    SOCKET_write(tcpipObj,'DIG:PIN LED3,0')
end

if p >=(100/7)*4
    SOCKET_write(tcpipObj,'DIG:PIN LED4,1')
else
    SOCKET_write(tcpipObj,'DIG:PIN LED4,0')
end

if p >=(100/7)*5
    SOCKET_write(tcpipObj,'DIG:PIN LED5,1')
else
    SOCKET_write(tcpipObj,'DIG:PIN LED5,0')
end

if p >=(100/7)*6
    SOCKET_write(tcpipObj,'DIG:PIN LED6,1')
else
    SOCKET_write(tcpipObj,'DIG:PIN LED6,0')
end

if p >=(100/7)*7
    SOCKET_write(tcpipObj,'DIG:PIN LED7,1')
else
    SOCKET_write(tcpipObj,'DIG:PIN LED7,0')
end

// Close connection with Red Pitaya

SOCKET_close(tcpipObj);

2.3.6.2.1.4.4. Code - LabVIEW

• Download Example

2.3.6.2.1.5. API Code Examples

Note

The API code examples don’t require the use of the SCPI server. Instead, the code should be compiled and executed on the Red Pitaya itself (inside Linux OS). Instructions on how to compile the code and other useful information are here.

2.3.6.2.1.5.1. Code - C API

/* Read analog voltage on slow analog input */

#include <stdio.h>
#include <stdlib.h>

#include "rp.h"

int main (int argc, char **argv) {
    float value [4];

    // Initialization of API
    if (rp_Init() != RP_OK) {
        fprintf(stderr, "Red Pitaya API init failed!\n");
        return EXIT_FAILURE;
    }

    // Measure each XADC input voltage
    for (int i=0; i<4; i++) {
        rp_AIpinGetValue(i, &value[i]);
        printf("Measured voltage on AI[%i] = %1.2fV\n", i, value[i]);
    }

    // Releasing resources
    rp_Release();

    return EXIT_SUCCESS;
}

2.3.6.2.1.5.2. Code - Python API

#!/usr/bin/python3
import rp

analog_in = [rp.RP_AIN0, rp.RP_AIN1, rp.RP_AIN2, rp.RP_AIN3]

# Initialize the interface
rp.rp_Init()

# Reset analog pins
rp.rp_ApinReset()

#####! Choose one of two methods, comment the other !#####

#! METHOD 1: Reading all values and selecting the appropriate

#for i in range(4):
#    # rp_ApinGetValue returns an array - [0, Input voltage in V, Input voltage RAW]
#    value = rp.rp_ApinGetValue(analog_in[i])[1]
#    print (f"Measured voltage on AI[{i}] = {value} V")


#! METHOD 2: Read just analog inputs

for i in range(4):
    # rp_AIpinGetValue returns an array - [0, Input voltage in V, Input voltage RAW]
    value = rp.rp_AIpinGetValue(i)[1]
    print (f"Measured voltage on AI[{i}] = {value} V")

# Release resources
rp.rp_Release()