Question

I have to control some hardware, which is controlled by a C interface.
The C interface is C++ header file, which contains some functions, one -called set_mirror()- which i need. This C file has also a int array, called voltage, which is used by set_mirror.
I am trying to use cython to build a python function, which implements a set_mir(volt) function. To do that, i have to set the voltage array, but i don’t know how to access it:

My pxy file:

cdef extern from 'mmdm_lin38usb.h':
    int voltage[40]
    int init_dac()
    void close_dac()
    void set_mirror()


init_dac()

def set_mir(volt):
    for i in range(40):
# Only for testing, how to access to int array.
        print voltage[i]

    if len(volt)!=40:
        raise "Need 40 values"
    else:
        volt=map(round,volt)
        volt=map(int,volt)
        voltage=volt
        set_mirror()

Answer 1

Is unclear what the final operation is : do you want to set 40 values from a volt python list
into an array of 40 ints ? I would suggest something like the following. If possible
don’t modify the global int array. Watch out the voltage array is local.

import clib

cdef extern from 'mmdm_lin38usb.h':
    int init_dac()
    void close_dac()
    void set_mirror(int *voltage)

init_dac()

cpdef set_mir(volt):
    cdef int voltage[40]

    if len(volt) != 40:
        raise ValueError("Need 40 values")

    for i from 0 <=  i < 40:
        print voltage[i]
        voltage[i] = int(clib.round(volt[i]))

    set_mirror(voltage)