FR2564665A1 - INPUT AND OUTPUT MULTIPLEXING DEVICE FOR AN ELECTRONIC CONTROL DEVICE COMPRISING A MICROCOMPUTER - Google Patents

Abstract

INPUT AND OUTPUT MULTIPLEXING DEVICE FOR ELECTRONIC CONTROL DEVICE, INCLUDING AN M MICROCOMPUTER, AN INPUT MATRIX (CLAV) AND AN OUTPUT MATRIX A AND MANAGED BY AN INTERRUPTION PROGRAM. BY MEANS OF AN RC LOW PASS FILTER THE INTERRUPTION PROGRAM PERFORMS THE FUNCTIONS OF A DIGITAL-ANALOGUE CONVERTER CONTROLLED BY PULSE WIDTH MODULATION. BY MEANS OF A CP COMPARATOR, THEN, SIMPLY, AN ANALOGUE-DIGITAL CONVERTER ALLOWING THE ACQUISITION OF ANALOGUE DATA BY THE MICRO-COMPUTER.

Description

Input and output multiplexer device for

  electronic control comprising a microcomputer. The present invention relates to an input and output multiplexing device for an electronic control device, comprising a microcomputer comprising a time counting device and an interrupt system activated by this time counting device, a matrix of input to which are connected the inputs of the microcomputer and some outputs, an output matrix to which are connected on the one hand the outputs connected to the input matrix and on the other hand to other outputs of the micro- computer, the

  device being managed by an interrupt program.

  A multiplexing device for an electronic programmer comprising a microcomputer is known from patent FR-2,340,649. This device comprises a matrix of switches connected on the one hand to three inputs of the microcomputer and two outputs thereof, outputs which are also connected to a digital display device with segments connected to a

  corresponding number of outputs of the microcomputer.

  In some applications, in particular in electronic control devices for household electrical appliances such as washing machines or dishwashers, in which regulation is carried out according to measured quantities, it is necessary to enter these measured values in analog form and to turn them into digital data

  likely to be processed by the microcomputer.

  It is possible to perform this data acquisition by means of a dedicated additional circuit comprising a digital-to-digital converter. Such a circuit is however relatively complex and expensive, characteristics which constitute a major disadvantage in an application to household appliances with a large diffusion, which

  can be considered mass articles.

  The present invention aims to perform the acquisition of analog data in a device of the type defined above, in addition to the multiplexing, by

  means as simple as possible.

  For this purpose, the device according to the invention further comprises a comparator whose input is intended to receive an analog voltage, whose other input is connected to an output of the microcomputer through a low-pass filter and whose output is connected to an input of the microcomputer, the time counter which activates the output connected to the low-pass filter, producing, with this low-pass filter, a digital-analog converter used to realize, by means of

  of said comparator, an analog converter

  digital of said analog voltage.

  The data acquisition function is therefore simply performed by means of a comparator. that is to say a simple differential amplifier, and a low-pass filter which can be realized simply by means of

  resistance and ability.

  The attached drawing represents. for example, a

embodiment of the invention.

  Figure 1 shows the electrical diagram of the device. Figure 2 shows the organization of the device software. The device essentially comprises a microcomputer M constituted for example by the microcomputer 7528 of NEC. This microcomputer has in its internal structure a time counting device or events Tim and an interrupt system activated by this counting device Tim. The set of n outputs Ss of the microcomputer M is connected to an output matrix A constituted for example by a set of m × n light-emitting diodes or multiplexed fluorescent display segments constituting a digital or alpha-numeric display device. . The set of m outputs Sd of the microcomputer M is also connected to the output matrix A, as well as to an input matrix Clav constituted for example by a set of m x i touch switches. The set of i inputs Ec of the microcomputer M is also connected to the input matrix Clay. The outputs Ss. Sd and the input Ec realize the functions of input multiplexing and

Release.

  An output Tout of the microcomputer M is further connected to a low-pass filter consisting of a resistor R and a capacitor C. whose output is connected to the input - of a comparator Cp. whose input * receives an analog voltage E i convert to signals

digital. -

  The output of the comparator Cp is connected to an In input

  of the microcomputer M. Analog conversion-

  digital voltage E is performed by the microcomputer M by means of the RC low-pass filter and

  of the comparator Cp. as will be described later.

  Figure 2 corresponds to the programming flowchart of the microcomputer, the operations being given in abbreviated form. The abreviations have the following meanings: Val = conversion result pt = multiplexing pointer cpt = rising edge counter F = variable indexed by pt responsible for activating one of the m outputs Sd H = variable indexed by pt responsible for activating the n outputs Ss G = variable indexed by pt receiving the values

i-inputs EC.

  At each interruption. that is, when the counting device Tim reaches a value

  programmed, the output Everything is complemented.-

  As can be seen from FIG. 2, on the falling edge of the output Tout (state 0) the value of the variable Val is loaded in the counter Tim, which is represented by Val-Tim. The pointer value of

  multiplexing pt is incremented by one unit (pt = pt + 1).

  If this value reaches the value m, that is to say the number of outputs Sd of the microcomputer, the multiplexing pointer pt is reset (yes pt = 0). In all cases the n outputs Ss of the microcomputer are set to zero (Ss = 0), while the m outputs Sd take the value F indexed by pt (Sd = F (pt), that is to say the value of the variable responsible for activating one of the m outputs Sd. As for the outputs Ss they take the value H indexed by pt (Ss = H (pt), that is to say the value of the variable receiving the values of the inputs Ec introduced by means of the input matrix Clay The value of the inputs Ec is stored in the variable G indexed by the pointer of

multiplexing pt (G (pt) = Ec).

  The rising edge of the All output (state 1) is used

  for acquisition and analog conversion-

  digital. When the front of the All output is rising, the value of the variable Val, which represents the result of the conversion, complemented by I (Val), is loaded into the counter Tim (Val-Tim). The value w of the rising edge counter Cpt is then incremented by one unit (Cpt = Cpt + 1). If the value of the counter Cpt reaches the value k (Cpt = k) the counter Cpt is reset (Cpt = 0). k is an integer such that k.T> R.C, where T is the time separating two successive rising edges of the output Tout. In this case, if the input In has a logic value of 1. the variable Val is decremented by one unit (Val = Val-1). In the case where the input In has the value O, the variable Val is incremented by one unit (Val = Val + 1). As already mentioned above, the outputs Ss, Sd and the input Ec perform the functions of input and output multiplexing, the change of multiplexing step being done by interruption. At the same time, the counter Tim activating the output Tout realizes, with the low-pass filter RC, a digital-analog converter operating by pulse width modulation present on the output Tout, thus making it possible to carry out, using the comparator Cp, a digital-to-digital converter. of the follower type, for the conversion of the analog signal E and its introduction in digital form in the microcomputer. The microcomputer M, the low-pass filter RC and the comparator Cp constitute a looped system in which the RC circuit introduces a certain delay which could compromise the stability of this looped system, but the delay kT provided by the rising edge counter. Cpt before adjusting the value of Val helps ensure the stability of the system. The result of the conversion Val is introduced into the microcomputer by the information transmitted to the input In and can be used by the latter.

  anyway desired and programmed.

  It is of course possible to swap the rising and falling edges of the All output. Similarly,

25646 5

  changes of the counter Cpt and the pointer pt can be incrementations or decrementations, of no value equal to 1 or any other different value

from scratch.

g

Claims (3)

claims   t. An input and output multiplexing device for an electronic control device, comprising a microcomputer (M) comprising   time counting (Tim) and an interrupt system.   activated by this time counting device, an input matrix (Clav) to which are connected the inputs (Ec) of the microcomputer and certain outputs (Sd), an output matrix (A) to which are connected by on the one hand the outputs (Sd) connected to the input matrix (Clav) -and on the other hand of other outputs (Ss) of the microcomputer, the device being managed by an interrupt program, characterized in that it further comprises a comparator (Cp) including an input   is intended to receive an analog voltage (E).   whose other input is connected to an output (Tout) of the microcomputer through a low-pass filter (RC) and whose output is connected to an input (In) of the microcomputer, the time counter. (Tim) who activates the output (All). connected to the low-pass filter (RC),   realizing, with this low-pass filter, a converter.   digital-analog used to achieve, by means   said comparator (Cp), an analog converter   digital of said analog voltage (E).   2. Device according to claim 1, characterized in that the analog-digital converter made is of the follower type.   3. Device according to claim 2, characterized in that it comprises a delay device (Cpt) delaying the tracking action of the analog-digital converter, so as to ensure the stability of the loop system constituted by the microcomputer,   the low-pass filter and the comparator.