DE10105857A1 - Cascadeable input output decoder for connection to a PC, etc. via serial, parallel or USB interface, has a modular design and onboard processor on first module to greatly speed input and output - Google Patents

Abstract

Interface for decoding a serial signal and converting it to a parallel signal (output) and vice versa. The interface is comprised of a series of cascaded modules so that it can have any number of inputs and outputs. A first module can be connected to a computer via a USB, parallel or serial port. The first module and all subsequent modules have two shift registers providing 16 parallel outputs. Using transistors at each output 16 inputs can be obtained. The first module has a processor for controlling communication with a PC or other central processing device. The modules are plugged together or cascaded. Power supply is via the first module.

Description

The invention relates to a circuit according to the preamble of claim 1.

So that different devices from a "center", for. B. a PC controlled you need an interface.

There are different methods of receiving a signal from a control unit, such as. B. a PC to send to a specific device.

• 1. It is known that the parallel port can be used to output parallel signals from the 8 bit lines and thus control 8 devices or functions of one device. A circuit that provides 8 inputs and outputs is the "parallel port I / O interface" from the magazine Elektor 04/2000 page 58.
  With the more complex circuit, the "Centronics-I / O-Port" from the book "306 circuits" page 458, it is possible to provide up to 32 outputs and 20 inputs.
• 2. A serial signal can also be converted via an interface in such a way that multiple inputs and outputs can be provided. For the serial interface The PC has two circuits, "8-channel D / O for RS232" and "8-channel D / I for RS232 ", which convert 8 outputs or 8 inputs accordingly. (Elektor 07/2000 p. 64/70)
• 3. You can also, as with the "Digital Multiple Train Control" from Märklin each device install a decoder, which is then connected to a signal line are connected. These have a specific address and are waiting Orders addressed to them and respond to them. So that can be very many devices and functions can be controlled.

However, this circuit has serious disadvantages:

• 1. The number of outputs and inputs, if any, are available severely limited and can only deal with large and complicated Circuit effort can be expanded. Also is the number of ICs needed Quite high. 11 circuits are used for the "Centronics I / O port alone needed. You also need a parallel port, which is usually the case with a PC is already occupied by the printer.
• 2. The same applies to the serial interfaces with restrictions and Price as for the parallel decoders.
• 3. If a decoder has to be built or purchased for each device that is very time consuming and costly.

My interface should have parallel inputs and outputs with little technical and Provide price expenditure. Easy communication with the  Control unit (e.g. PC) via a serial interface that can be flexibly connected to the parallel one and serial port can be connected. The number of connections for Devices should be easily expandable via a modular design.

My decoder is a module. The first module has a processor which Communication with the headquarters takes over and on various conditions adapts. A connection is possible to the serial, parallel and USB port. This module and all other modules each have two shift registers Provide 16 outputs. The output takes place in parallel. With the help of Transistors at each output create 16 inputs. The shift registers will be controlled by the processor on the first module, which enables a very quick input and Output is possible. When new data is accepted, the outputs are not changed when the data has been read in completely.

Modules can be used as often as required, e.g. B. connected via a plug, one after the other (cascaded). This increases the number of connections per module by 16 extended. The processor automatically detects how many modules are connected. It is also possible to connect a module to the PC without a processor.

A DC or AC voltage between 5 and 20 volts can be used for the power supply be connected. The first module generates the required one Voltage for the ICs.

The costs are due to the small number of components and their small number Prices very small. Due to the modular design, the circuit can be easily connected to the Adapt needs. The costs are linear.

It is also possible to connect other modules to a decoder, which can switch larger loads or take on special tasks. (e.g. relay Module)  

Circuit and connection examples are shown in the drawings described in more detail below.

Show it

Fig. 1: Circuit of the 16-bit decoder module with processor

Fig. 2: Circuit of another decoder module

I use the IC 4094 (IC1 and IC2) as a shift register. This circuit is an 8-bit shift register with additional memory register and three Output states. With the help of the memory register, the outputs can last as long kept in the same state until the new information is completely in the Shift registers have been transferred. Only then will the data from the Shift registers copied into the memory register (IC1 / 2 STR).

There are two shift registers (IC1 and IC2) on one module, which deliver a total of 16 outputs.

The processor ( Fig. 1 IC3) shifts data serially into the shift register (IC1). For this purpose, a bit is transferred to (IC1 D) with a clock pulse (IC1 / IC2 CLK) and the data in the shift register is shifted further. The 8th bit in IC1, which also appears at the cascading output QS *, is forwarded to the data input (D) of IC2 and inserted there.

The cascading signal (QS *) from IC2 is connected on the one hand to the power strip and on the other hand to the base of T1. If no further module is connected and there is no connection between ground and switch, then T2 is closed. The cascading signal is thereby forwarded to the processor via T1. If the contact between ground and switch is closed because another decoder module ( Fig. 2) is connected, then T2 is closed. No current flows through T2 and therefore not through T1. However, the cascading signal ( Fig. 1 Reset) is sent from the next connected module ( Fig. 2) to the processor.

On further modules there are only 2 shift registers ( Fig. 2), each of which is connected to the clock (CLK), data (QS * → D) and the apply signal (STR).

Any number of modules ( Fig. 2) can be connected and you get 32, 48, 64 or more outputs. A certain bit pattern can be used to determine after how many clock pulses this pattern appears again on the processor ( Fig. 1 IC3 PB4). The number of outputs that are available is now available.

Another advantage of this IC 4094 is that the outputs are activated or deactivated (tristate) can be (IC1 / 2 OE). So short impulses can easily be sent to the Outputs are generated.

A transistor (T2-T10, T11-T18) is connected to its base at each data output (Q1-Q8) of a shift register. The collector is connected with the collectors of the other transistors to the processor ( Fig. 1 IC3 PB2). If the emitter of a transistor is now connected to ground and the corresponding output from the shift register to which the transistor is connected is activated, the input line ( Fig. 1 IC2 PB2) is also connected to ground. This gives the processor information about the state of the input. In this way you get an input for each output.

Claims (8)

1. Interface for decoding a serial signal into parallel signals (outputs) and vice versa (inputs) ( Fig. 2), characterized in that the interface is composed of cascadable modules and can therefore have any number of inputs and outputs. 2. Interface according to claim 1, characterized in that the decoding by shift registers (IC1 and IC2). 3. Interface according to claim 1 and 2, characterized in that the control of the interface with a processor ( Fig. 1 IC3) and this takes over the communication to the outside. 4. Interface according to claim 3, characterized in that the processor ( Fig. 1 IC3) program memory, SRAM and ROM already contains. 5. Interface according to claims 1-3, characterized in that the processor ( Fig. 1 IC3) can be connected to any port (LPT, COM, USB) 6. Interface according to claim 4-5, characterized in that the communication and control using the software in the processor ( Fig. 1 IC3). 7. Interface according to claims 1-7, characterized in that the input and Output connections of the modules and their number by the processor to provide. 8. Interface according to claims 1-8, characterized in that on one Decoder module also other modules for different tasks can be connected.