JP2753542B2 - Barcode detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a non-decode type bar code scanner which only photoelectrically reads an image of a bar code mark and does not have a function of decoding a bar code. The present invention relates to a barcode detection device including:

[Summary of the Invention] The present invention is directed to a bar code recognition process based on a level change of two levels of data corresponding to white / black from a non-decode type bar code scanner as described above by a general data processing. In a data processing device that is also performed by a processor for processing, a process of developing level change information in a memory;
A dedicated circuit for performing an end margin detection process is provided, and on the condition that the end margin is detected, the processor is instructed to perform a decoding process based on the level change information developed in the memory, thereby reducing the load on the processor. This is to increase the processing speed of the entire apparatus.

[Prior Art] Conventionally, in a data processing device such as an electronic register provided with a non-decode type bar code scanner, as shown in FIG. The image data is stored in the input buffer 2. Then, the edge detection circuit 4 checks the change state of the level of the image data for each sampling clock from the clock generator 3, and notifies the bar width counter 5 of the change state each time the level changes, and continuously outputs the same data. At the same time, the CPU 6 counts the sampling clock during the period of the level and interrupts the CPU 6.

Due to this interrupt, the CPU 6 reads the count value of the bar width counter 5 and the level information and sequentially develops them in the memory 7. Further, the CPU 6 sequentially compares the previous count value developed in the memory 7 with the current count value of the bar width counter 5, and detects an end margin based on the comparison result.

Then, the CPU 6 repeats the above-described processes until the end margin is detected. When the end margin is detected, the CPU 6 performs a decoding process based on a plurality of sets of count values and level information developed in the memory 7. .

[Problems to be Solved by the Invention] However, if a series of barcode reading processes is delayed, data may be missed, and the like.
U6 does not have time to perform other processing such as registration processing based on the read barcode during the reading processing period, and in fact, it performs only reading processing, and the use efficiency of CPU 6 is poor, and This has led to a reduction in the overall processing speed.

This is thought to be due to an excessive load on the CPU.

Therefore, if it is possible to reduce the load on the CPU by processing some of the processing performed by the CPU using components other than the CPU, it can be inferred that a decrease in the processing speed of the entire device would be avoided. If processing other than processing suitable for processing by the CPU, such as processing, is performed by other components, problems remain in terms of, for example, a balance between avoiding a reduction in processing speed and increasing costs due to the addition of components.

In other words, processing that is considered to be faster and not costly if processing with other components such as processing to expand the count value and level information to memory, end margin detection processing, etc. Being able to do so by elements is a new technical challenge.

An object of the present invention is to enable decoding of data to be decoded to a memory and detection of an end margin by using components other than a CPU (processor).

[Means for Solving the Problems] The means of the present invention are as follows.

Scanner a (refer to the block diagram in FIG. 1, the same applies hereinafter)
Reads the scanned barcode image as two levels of data corresponding to white / black.

The detection circuit b detects a level change state of data from the scanner a at a timing of a clock of a predetermined cycle.

The counter c counts until the next level change is detected by the detection circuit b.

After buffering each count value of the counter c, the transfer control circuit d sequentially performs DMA transfer to a predetermined memory.

The instruction circuit e sequentially compares the previous count value buffered by the transfer control circuit d with the current count value of the counter, and when the current count value with respect to the previous count value becomes equal to or more than a predetermined ratio, It outputs an end margin detection signal and instructs each count value DMA-transferred to a predetermined memory to be decoded into barcode data.

[Operation] The operation of the means of the present invention is as follows.

Now, the bar code mark is being scanned by the scanner a, and a voltage signal of “0” volt corresponding to “white” of the bar code mark and a voltage signal of “5” volt corresponding to “black” of the bar code mark. Is continuously input.

Then, the detection circuit b detects the state of the level change of the data from the scanner a at the timing of the clock of the predetermined cycle, and outputs it to the counter c.

The counter c counts until the next level change is detected by the detection circuit b, that is, while read data of the same level continues. Therefore, when the next level change (“0” volt → “5” volt or “5” volt → “0” volt) is detected, the count value of the counter c is the “white bar” of the bar code mark. , "Black bar".

On the other hand, when the next level change is detected by the detection circuit b, the transfer control circuit d uses the count value of the counter c at that time as the previous count value corresponding to the width of the immediately preceding bar. After buffering, the data is DMA-transferred to a predetermined memory.

Then, the instruction circuit e sequentially compares the buffered previous count value and the current count value currently being counted up by the counter c, for example, at a timing of a clock of a predetermined cycle. As a result of this comparison, the current count value with respect to the previous count value is equal to or greater than a predetermined ratio (for example, the ratio is determined in consideration of the minimum width, the maximum width, and the like of a white bar and a black bar of a standardized barcode). ), That is, when the continuous reading width of “white” or “black” currently being read with respect to the previous bar width has exceeded a predetermined ratio, an end margin detection signal is sent to a processor or the like. Then, it instructs a processor or the like to decode each count value corresponding to each bar width DMA-transferred to a predetermined memory into barcode data.

Therefore, the components other than the processor can load the decoding target data into the memory and detect the end margin.

Embodiment An embodiment will be described below with reference to FIG.

FIG. 2 is a block diagram of an interface circuit for a bar code scanner, which has a non-decode type bar code scanner 1, an input buffer 2, and has a start margin detecting function, a data expanding function, and an end margin detecting function. After the start margin is detected, the substantial data expansion processing and the end margin detection processing are performed simultaneously and in parallel.

The start margin detection processing is executed by the level detection circuit 8, the start margin counter 9, the start margin register 10, and the first comparator 11.

The data expansion processing is executed by the edge detection circuit 4, the bar width counter 5, the memory 7, the latch 12, the DMA control logic circuit 13, and the DMA controller 14.

The end margin detection processing includes an edge detection circuit 4, a bar width counter 5, a latch 12, an end margin register 1
5, executed by the multiplier 16 and the second comparator 17.

The illustrated CPU 6 is a general-purpose CPU that performs various processes in addition to the decoding process described below. The clock generator 3 is used in all the above processes,
It is not used as the basic clock of U6 and is not shown.
A clock generator for CPU 6 is provided separately.

The non-decode type barcode scanner 1 optically reads an image, photoelectrically converts the image, and converts the image into a “High (hereinafter abbreviated as“ H ”)” level and a “Low (hereinafter abbreviated as“ L ”)” level. The scanner itself does not have a function of decoding the read barcode image data only by inputting as value data.

The input buffer 2 corrects the level of the binary data from the non-decode type barcode scanner 1 to a predetermined level, buffers the corrected level, and outputs it to the edge detection circuit 4 and the level detection circuit 8.

The clock generator 3 generates a clock higher in frequency than the basic clock of the CPU 6, and outputs an edge detection circuit 4, a bar width counter 5, a level detection circuit 8, a start margin
Output to counter 9.

The edge detection circuit 4 samples the image data input via the input buffer 2 based on the clock from the clock generator 3 and changes the data level (“H” → “L” or “L” → “ H "), and when the level changes, the changed data (" H "or" L ") is output to the bar width counter 5 as a reset signal, and the data is output to the latch 12 as a latch signal. And outputs it to the DMA control logic circuit 13 as a DMA transfer start signal.

The bar width counter 5 counts the clock from the clock generator 3 until the next reset signal is input from the edge detection circuit 4.

The level detection circuit 8 samples the image data input via the input buffer 2 based on the clock from the clock generator 3 and detects the level of the sampled data.

The start margin counter 9 includes a level detection circuit 8
Thus, only while the “L” level corresponding to “white” is detected, the clock from the clock generator 3 is counted, and the count value is sequentially output to the first comparator 11.

When the non-decode type barcode scanner 1 is connected to the present interface circuit, the minimum value of the start margin is set in the start margin register 10 by the CPU 6. Note that this minimum value is calculated in consideration of the scanning speed of the non-decode type barcode scanner 1 and the width (white portion) between the standardized barcode bars.

The first comparator 11 stores the count value from the start margin counter 9 and the start margin register 10
The start margin detection signal is output to the DMA control logic circuit 13 when the count value matches the minimum value.

The latch 12 detects “H” detected by the level detection circuit 8,
Alternatively, the “L” level information is latched. Latch 12
Latches the current count value in the bar width counter 5 together with an overrun flag described later, based on the latch signal from the edge detection circuit 4. At this time, the bar width counter 5 latches the count value,
The reset is immediately performed based on the reset signal, and the next count-up is started. Therefore, the latch 12
The level information, the count value, and the overrun flag corresponding to the previous one “white” or “black” bar are latched.

Based on the DMA transfer start signal from the edge detection circuit 4, the DMA control logic circuit 13
14 manages DMA transfer processing.

DMA controller 14 is a DMA control logic circuit
Via 13, a DMA transfer process from the latch 12 to the memory 7 is controlled.

When the non-decode barcode scanner 1 is connected to the present interface circuit, the CPU 6 sets a predetermined ratio in the end margin register 15. This ratio is the bar code space (white) / mark (black)
Is the minimum and maximum ratio. That is, by using the relative ratio of the minimum and maximum ratio of the space (white) / mark (black), the end margin can be detected without being affected by the scanning speed.

The multiplier 16 multiplies the previous count value latched by the latch 12 by the ratio set in the end margin register 15 to scale the magnification, and outputs the scaled value to the comparator 17.

The comparator 17 sequentially compares the scaled previous count value from the multiplier 16 with the count value currently being counted up from the bar width counter 5. When the current count value matches the previous count value, the CPU 6
An end margin detection signal is output to the interrupt terminal of.

 Next, the data expansion operation will be described in detail.

This data expanding operation is substantially performed after the first comparator 11 outputs the start mercidin detection signal.

That is, when the barcode mark is scanned by the scanner 1, the level detection circuit 8, the start margin
The start margin detection operation by the counter 9, the start margin register 10, and the first comparator 11 is started. In parallel with this start margin detection operation, the count operation by the bar width counter 5 based on the data from the edge detection circuit 4 and the latch operation by the latch 12 are also performed, but the DMA control logic circuit 13 outputs the start margin detection signal. Until the data is detected, data is not read from the latch 12, and the DMA transfer operation and the end margin detection operation are not performed.

After the start mercidin detection signal is detected, the DMA control logic circuit 13 outputs a DMA request signal to the DMA controller 14 every time the DMA transfer start timing signal is input from the edge detection circuit 4. .

Then, the DMA controller 14 outputs an acknowledge signal to the DMA control logic circuit 13 and then DMA-transfers the data in the latch 12 to the memory 7.

At this time, the DMA control logic circuit 13 disables the DMA request, and if the latch 12 receives data before the end of the DMA transfer, the overrun
The flag is set, and if no data is received before the end of the DMA transfer, the overrun flag is reset. That is, the overrun flag indicates whether or not the data is zero. How to use this overrun flag will be described later.

By such a DMA transfer, the CPU 6 does not need to perform data expansion processing on the memory.

 Next, the operation of detecting the end margin will be described in detail.

Now, in the latch 12, one bar (space (white) bar, black bar) in one unit of barcode mark read last time is displayed.
Are latched, a start margin detection signal is already output from the first comparator 11, and data can be read from the latch 12.

In this case, the previous count value latched by the latch 12 is also output to the multiplier 16.

Then, the multiplier 16 multiplies the previous count value by the ratio in the end margin register 15 and outputs the multiplied value to the second comparator 17.

The second comparator 17 sequentially compares the multiplied value with the count value currently being counted up sequentially transferred from the bar width counter 5 based on the clock. That is, the second comparator 17 has a fixed value until the edge detection circuit 4 detects the next edge. latch
A comparison between the multiplied value obtained by scaling the count value corresponding to the previous one bar in 12 and each count value from the bar width counter 5 which is currently counting up corresponding to one bar is performed. , Sequentially in synchronization with each clock.

The second comparator 17 outputs an end margin detection signal to the interrupt terminal of the CPU 6 assuming that the end margin area has been scanned when the current count value is sequentially counted up and coincides with the multiplied value. I do.

As described above, the end margin detection process is also performed only by the dedicated circuit, and the CPU 6 is not involved at all.

When the end margin detection signal is input, the CPU 6 performs a decoding process based on the data DMA-transferred to the memory 7, confirms a normal reading based on the overrun flag and the like, and Stops the reading process of the barcode. Here, if the normal reading is not performed, that is, even if the end margin detection is incorrect, the memory expansion processing and the end margin detection processing described above are continued. After waiting, it is possible to determine the stop / continuation of the barcode reading process for one unit.

As described above, the start margin detection processing, the memory expansion processing, and the end margin detection processing, which require extremely high speed, which need to be sequentially performed in synchronization with the clock,
Since each is executed by a separate circuit group from CPU6, CP
U6 does not need to perform any processing until the end margin is detected, greatly reducing the load on the CPU.

[Effects of the Invention] According to the present invention, components other than the CPU (processor) can load the decoding target data into the memory and detect the end margin, and reduce the load on the processor for reading the barcode. More data processing can be performed, and the processing speed of the entire apparatus can be increased.

[Brief description of the drawings]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a block diagram of an embodiment, and FIG. 3 is a block diagram showing a conventional technique. 1 Non-decode barcode scanner, 3 Clock generator, 4 Edge detection circuit, 5 Bar width counter, 7 Memory, 12 Latch, 13 DM
A control logic circuit, 14 …… DMA controller,
15 ... End margin register, 16 ... Multiplier, 17 ...
Second comparator.

Claims (1)

(57) [Claims] 1. A scanner for reading a scanned barcode image as two-level data corresponding to white / black, and a detecting circuit for detecting a level change state of data from the scanner at a clock timing of a predetermined cycle. A counter that counts until the next level change is detected by the detection circuit, a transfer control circuit that buffers each count value of the counter, and sequentially DMA-transfers the data to a predetermined memory; The ringed previous count value is sequentially compared with the current count value of the above counter, and when the current count value with respect to the previous count value becomes equal to or more than a predetermined ratio, an end margin detection signal is output, and a predetermined memory is output. And an instruction circuit for instructing each of the DMA-transferred count values to be decoded into barcode data. A bar code detection device comprising: