We have found 2 software records in our database eligible for .xls to .ecsv file format conversion.
It looks like that Microsoft Excel supports ECSV format (Encapsulated Comma Separated Value) just fine, so you can convert data from .xls spreadsheets and save it as .ecsv simply with the File ► Save as.. function.
Same can be likely also achieved with some open source Excel alternative, such as Calc program from Ooo or LibreOffice.
XLS
Files with xls extension are best known as spreadsheets from Microsoft Excel. A spreadsheet is basically a grid of cells sorted in rows and columns. Each cell can contain text, numeric or formula data. Excel XLS spreadsheets can be opened in most other similar programs, such as OpenOffice.org Calc.
ECSV
Files with ecsv file extension can be mainly found as data files saved in the Encapsulated Comma Separated Value format.