How to Remove Initial Letter from String in Studio 5000 Professional

The Painterman asked whether reducing the length of Scan_PNUM.len would eliminate characters from the beginning or end of the string. He expressed concern about avoiding empty spaces at the start of the string. In actuality, decreasing .LEN will trim characters from the end of the string. Conversely, increasing it will append characters (potentially blank spaces unless alterations have been made to the .DATA[] values). Utilize the built-in commands, such as DELETE or MID, to remove characters, and the length will be automatically adjusted to accommodate the changes. This will ensure a seamless adjustment without any unwanted empty spaces.

• 10-09-2024
• plvlce

The painterman noted that in Scan_PNUM.DATA[0], the letter "P" is displayed. To convert the ASCII to Allen-Bradley, the barcode scanner can be utilized. If 1 is removed from Scan_PNUM.len, it is important to determine whether this change will occur at the front end or the back end to avoid an empty space at the beginning of the string. Grateful for the advice received, incorporating a setup to examine the .DATA[] part of the tag was not initially considered. The MID instruction, suggested by @joseph_e2, sets a Start parameter value of 2, extracting string data starting from the second character (ScanString.DATA[1] since ScanString.DATA[0] represents the first character). The DELETE instruction effectively removes data based on the Qty and Start input parameters, subsequently adjusting the string length. Alternatively, the COP instruction could be used as follows: EQU ScanString.DATA[0] 80 COP ScanString.Data[1] ScanString[0] 80 SUB ScanString.LEN 1 ScanString.LEN However, it is recommended to utilize the built-in string handlers for better results. Additionally, considering adding a test for a zero-length string may be beneficial.

• 10-09-2024
• drbitboy

drbitboy explained the functionality of the MID instruction suggested by @joseph_e2, which has a Start parameter set to 2. This means that it will extract the string data starting from the second character of the string, specifically from ScanString.DATA[1], as the first character is at ScanString.DATA[0]. The DELETE instruction, on the other hand, removes data based on the Qty and Start input parameters, adjusting the string length accordingly. Alternatively, the COP instruction can achieve a similar outcome, though it is recommended to utilize the built-in string handlers for better results. It is also advisable to include a test for zero-length strings. When using the DELETE instruction, it will remove .DATA[0] entirely and shift all subsequent .DATA[#] values up, effectively turning DATA[1] into DATA[0]. Additionally, if the string is replaced back into itself, there may be a repetition of the last character since the new string is one character shorter. The trigger for this process revolves around checking if the string length is not equal to zero.

• 11-09-2024
• painterman

Using the DELETE instruction proved to be a wise decision due to its speed and efficiency. I conducted a test by deleting a copy of the string and replacing it with itself. Although the trailing character remained in the .DATA array, the .LEN was appropriately shortened. This means that the character only shows up when directly viewing the SINT array. An important observation from the test was that even though .DATA[9] extended beyond the new 9-character string, it retained its original value of '9' instead of being replaced by '$00'.

• 12-09-2024
• joseph_e2

In a recent discussion, joseph_e2 pointed out the efficiency of using the DELETE instruction for removing characters from a string. After running a test with the DELETE instruction, it was observed that while the trailing character remains in the .DATA array, the .LEN is shortened, making it visible only when directly looking at the SINT array.View attachment 69643The outcome of the test can be seen here:View attachment 69644It is worth noting that .DATA[9] retains its value even though it is located past the end of the newly formed 9-character string. Considering this, it is possible to utilize another delete function to specifically remove the last character based on the original length of the string.

• 12-09-2024
• painterman

The painter mentioned using another delete function to remove the last character based on the original length of the string. However, this approach is incorrect. Once the length of the string changes, the character at the original last position becomes irrelevant. This is because it is no longer considered part of the string, even though it was at the ninth position based on the original length.

• 12-09-2024
• drbitboy

In a discussion, drbitboy highlighted that changing the length of a string can impact the characters at specific positions. For example, if the length is adjusted from 9 to 8, the character at the ninth position becomes irrelevant. This is important to consider when working with strings in a PLC, especially when searching for an exact match as it may include the last character despite the change in length. It's essential to understand how these adjustments affect the overall functionality of the code.

• 12-09-2024
• painterman

I recently delved into string manipulation and discovered a common issue with residual characters, such as COP, being left behind after using instructions like DELETE or MID to shorten a string. Although the LEN parameter adjusts accordingly, the SINT array retains the original characters beyond the new string length. This can result in only the "legit" portion of the string being visible online, unless you expand the .DATA tag to reveal the additional characters. While built-in comparison instructions like EQU only focus on the "legit" characters, direct manipulation of the SINT array may necessitate some cleanup. For example, our Maple Systems HMI disregards the .LEN tag and instead relies on the first '$00' as the string terminator.

• 12-09-2024
• joseph_e2

When comparing string data types, whether using a basic EQU comparison or a custom comparison that iterates over the .DATA[] SINT array while utilizing the .LEN attribute of the SYRING data type, the elements beyond .DATA[.LEN] are not relevant. Modifying the .LEN parameter after reducing it by 1 using the DELETE instruction is an error. Even if you overwrite the final "duplicate" character's value, simply removing the excessive 'P' will leave the string unchanged as if the barcode initially arrived on the serial line without the prefix. Remember that the replacement value may not necessarily be an improvement over the duplicated value. As @joseph_e2 previously mentioned, eliminating two instructions and any leading 'P' will result in the same string without altering its essence.

• 12-09-2024
• drbitboy

In this experiment, we will be demonstrating the process of manipulating string tags in a PLC program. Three string tags will be created and initialized as follows: 'four' as '4', 'ScanSim' as 'P1234', and 'ScanString' as '$00$00$00$00$00$00$00$00'. The program will consist of the following rungs: - MOV ScanSim ScanString (simulating a barcode read) - Performing operations to manipulate the ScanString tag to extract specific values - MOV -99 result to ensure proper execution of the next command - Using the FIND command to search for the sub-string 'four' within ScanString By running this program, we will be able to verify that the '4' value within ScanString is not part of the actual string tag but rather a SINT value represented as 52 decimal (34H).

• 12-09-2024
• drbitboy