Document passing arguments to main() (espressif#408)

* Document passing arguments to main()

Addresses espressif#406]

README.md

@@ -416,6 +416,20 @@ Note that not every serial program supports the unusual ESP8266 74880bps "boot l
 
 Running `esptool.py --trace` will dump all serial interactions to the standard output (this is *a lot* of output). This can be helpful when debugging issues with the serial connection, or when providing information for bug reports.
 
+## Using esptool.py from Python
+
+esptool.py can easily be integrated into Python applications or called from other Python scripts.
+
+While it currently does have a poor Python API, something which [#208](https://github.com/espressif/esptool/issues/208) will address, it allows for passing CLI 
+arguments to `esptool.main()`. This workaround makes integration very straightforward as you can pass exactly the 
+same arguments as you would on the CLI.
+
+```python
+command = ['--baud', '460800', 'read_flash', '0', '0x200000', 'flash_contents.bin']
+print('Using command %s' % ' '.join(command))
+esptool.main(command)
+```
+
 ## Internal Technical Documentation
 
 The [repository wiki](https://github.com/espressif/esptool/wiki) contains some technical documentation regarding the serial protocol and file format used by the ROM bootloader. This may be useful if you're developing esptool.py or hacking system internals:

esptool.py

@@ -2548,7 +2548,8 @@ def main(custom_commandline=None):
     Main function for esptool
 
     custom_commandline - Optional override for default arguments parsing (that uses sys.argv), can be a list of custom arguments
-    as strings.
+    as strings. Arguments and their values need to be added as individual items to the list e.g. "-b 115200" thus
+    becomes ['-b', '115200'].
     """
     parser = argparse.ArgumentParser(description='esptool.py v%s - ESP8266 ROM Bootloader Utility' % __version__, prog='esptool')