diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..e77c69b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+venv
+build
+dbibackend.egg-info
+*__pycache__*
\ No newline at end of file
diff --git a/README.md b/README.md
index ac31484..99e4c3e 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,8 @@
-DBI backend
-===========
+# DBI backend
 
 PC-side server for games installation into Nintendo Switch
 
-Requirements
-------------
+## Requirements
 Host:
 
 - libusb
@@ -14,8 +12,12 @@ Host:
 Nintendo Switch:
 - DBI v202+
 
-Usage
------
-* Run server `python3 dbibackend.py tites_dir_path`
-* Run DBI and then Installation titles from USB
-* Install files
+## Usage
+
+1. Git clone this repository `git clone git@github.com:lunixoid/dbibackend.git`
+1. `cd dbibackend`
+1. Run `sudo bash` to start a bash shell in case you are using zsh or fish.
+   You need root privileges to access the USB device.
+1. Run `. ./env.sh` to set up the environment.
+   This will set up the python environment and its dependencies.
+1. Run `dbi -d <PATH_TO_ROM_DIRERCTORY>` 
diff --git a/dbibackend/dbi.py b/dbibackend/dbi.py
new file mode 100644
index 0000000..3fb095c
--- /dev/null
+++ b/dbibackend/dbi.py
@@ -0,0 +1,210 @@
+import usb.core
+import usb.util
+import struct
+import sys
+import time
+import argparse
+import logging
+import os
+from enum import IntEnum
+from collections import OrderedDict
+from pathlib import Path
+
+
+log = logging.getLogger(__name__)
+log.addHandler(logging.StreamHandler(sys.stdout))
+log.setLevel(logging.INFO)
+
+BUFFER_SEGMENT_DATA_SIZE = 0x100000
+
+
+class CommandID(IntEnum):
+    EXIT = 0
+    LIST_DEPRECATED = 1
+    FILE_RANGE = 2
+    LIST = 3
+
+
+class CommandType(IntEnum):
+    REQUEST = 0
+    RESPONSE = 1
+    ACK = 2
+
+
+class UsbContext:
+    def __init__(self, vid: hex, pid: hex):
+        dev = usb.core.find(idVendor=vid, idProduct=pid)
+        if dev is None:
+            raise ConnectionError(f'Device {vid}:{pid} not found')
+
+        dev.reset()
+        dev.set_configuration()
+        cfg = dev.get_active_configuration()
+
+        self._out = usb.util.find_descriptor(
+            cfg[(0, 0)],
+            custom_match=lambda ep: usb.util.endpoint_direction(ep.bEndpointAddress) == usb.util.ENDPOINT_OUT
+        )
+        self._in = usb.util.find_descriptor(
+            cfg[(0, 0)],
+            custom_match=lambda ep: usb.util.endpoint_direction(ep.bEndpointAddress) == usb.util.ENDPOINT_IN
+        )
+
+        if self._out is None:
+            raise LookupError(f'Device {vid}:{pid} output endpoint not found')
+        if self._in is None:
+            raise LookupError(f'Device {vid}:{pid} input endpoint not found')
+
+    def read(self, data_size, timeout=0):
+        return self._in.read(data_size, timeout=timeout)
+
+    def write(self, data, timeout=0):
+        self._out.write(data, timeout=timeout)
+
+
+def process_file_range_command(data_size, context, cache=None):
+    log.info('File range')
+    context.write(struct.pack('<4sIII', b'DBI0', CommandType.ACK, CommandID.FILE_RANGE, data_size))
+    file_range_header = context.read(data_size)
+    range_size = struct.unpack('<I', file_range_header[:4])[0]
+    range_offset = struct.unpack('<Q', file_range_header[4:12])[0]
+    nsp_name_len = struct.unpack('<I', file_range_header[12:16])[0]
+    nsp_name = bytes(file_range_header[16:]).decode('utf-8')
+    if cache is not None and len(cache) > 0:
+        if nsp_name in cache:
+            nsp_name = cache[nsp_name]
+
+    log.info(f'Range Size: {range_size}, Range Offset: {range_offset}, Name len: {nsp_name_len}, Name: {nsp_name}')
+
+    response_bytes = struct.pack('<4sIII', b'DBI0', CommandType.RESPONSE, CommandID.FILE_RANGE, range_size)
+    context.write(response_bytes)
+
+    ack = bytes(context.read(16, timeout=0))
+    cmd_type = struct.unpack('<I', ack[4:8])[0]
+    cmd_id = struct.unpack('<I', ack[8:12])[0]
+    data_size = struct.unpack('<I', ack[12:16])[0]
+    log.debug(f'Cmd Type: {cmd_type}, Command id: {cmd_id}, Data size: {data_size}')
+    log.debug('Ack')
+
+    with open(nsp_name, 'rb') as f:
+        f.seek(range_offset)
+        curr_off = 0
+        remaining_size = range_size
+
+        while remaining_size > 0:
+        
+            chunk_size = min(BUFFER_SEGMENT_DATA_SIZE, remaining_size)
+            buf = f.read(chunk_size)
+        
+            if not buf:
+                log.warning("Unexpected EOF reached before reading complete range.")
+                break
+        
+            context.write(data=buf, timeout=0)
+            curr_off += chunk_size
+            remaining_size -= chunk_size
+
+
+def process_exit_command(context):
+    log.info('Exit')
+    context.write(struct.pack('<4sIII', b'DBI0', CommandType.RESPONSE, CommandID.EXIT, 0))
+    sys.exit(0)
+
+
+def process_list_command(context, work_dir_path):
+    log.info('Get list')
+
+    cached_roms = OrderedDict()
+    for dirName, subdirList, fileList in os.walk(work_dir_path):
+        log.debug(f'Found directory: {dirName}')
+        for filename in fileList:
+            if filename.lower().endswith('.nsp') or filename.lower().endswith('nsz') or filename.lower().endswith('.xci'):
+                log.debug(f'\t{filename}')
+                cached_roms[f'{filename}'] = str(Path(dirName).joinpath(filename))
+
+    nsp_path_list = ''
+    for rom in cached_roms.keys():
+        nsp_path_list += f'{rom}\n'
+    nsp_path_list_bytes = nsp_path_list.encode('utf-8')
+    nsp_path_list_len = len(nsp_path_list_bytes)
+
+    context.write(struct.pack('<4sIII', b'DBI0', CommandType.RESPONSE, CommandID.LIST, nsp_path_list_len))
+
+    ack = bytes(context.read(16, timeout=0))
+    cmd_type = struct.unpack('<I', ack[4:8])[0]
+    cmd_id = struct.unpack('<I', ack[8:12])[0]
+    data_size = struct.unpack('<I', ack[12:16])[0]
+    log.debug(f'Cmd Type: {cmd_type}, Command id: {cmd_id}, Data size: {data_size}')
+    log.debug('Ack')
+
+    context.write(nsp_path_list_bytes)
+    return cached_roms
+
+
+def poll_commands(context, work_dir_path):
+    log.info('Entering command loop')
+
+    cmd_cache = None
+    while True:
+        cmd_header = bytes(context.read(16, timeout=0))
+        if not cmd_header.startswith(b'DBI0'):  # Tinfoil USB Command 0
+                continue
+        
+        cmd_type = struct.unpack('<I', cmd_header[4:8])[0]
+        cmd_id = struct.unpack('<I', cmd_header[8:12])[0]
+        data_size = struct.unpack('<I', cmd_header[12:16])[0]
+
+        log.debug(f'Cmd Type: {cmd_type}, Command id: {cmd_id}, Data size: {data_size}')
+
+        if cmd_id == CommandID.EXIT:
+            process_exit_command(context)
+        elif cmd_id == CommandID.LIST:
+            cmd_cache = process_list_command(context, work_dir_path)
+        elif cmd_id == CommandID.FILE_RANGE:
+            process_file_range_command(data_size, context=context, cache=cmd_cache)
+        else:
+            log.warning(f'Unknown command id: {cmd_id}')
+            process_exit_command(context)
+
+
+def connect_to_switch():
+    while True:
+        try:
+            switch_context = UsbContext(vid=0x057E, pid=0x3000)
+        except ConnectionError as e:
+            log.info('Waiting for switch')
+            time.sleep(1)
+            continue
+        return switch_context
+
+
+def get_args(args):
+    parser = argparse.ArgumentParser(
+        prog='dbibackend',
+        description='Install local titles into Nintendo switch via USB',
+        add_help=True
+    )
+    parent_group = parser.add_argument_group(title='Command line params')
+    parent_group.add_argument('-d','--rom-dir', type=Path, required=True,
+                              help='Path to directory with NSP/NSZ/XCI files')
+    parent_group.add_argument('--debug', action='store_true', default=False, required=False,
+                              help='Enable debug output')
+    return parser.parse_args(args)
+
+
+def main():
+    args = get_args(sys.argv[1:])
+    if args.debug:
+        log.setLevel(logging.DEBUG)
+
+    if not Path(args.rom_dir).is_dir():
+        raise NotADirectoryError('Specified path must be a directory')
+
+    poll_commands(
+        connect_to_switch(),
+        work_dir_path=args.rom_dir
+    )
+
+
+if __name__ == '__main__':
+    main()
diff --git a/env.sh b/env.sh
new file mode 100755
index 0000000..8fbbf39
--- /dev/null
+++ b/env.sh
@@ -0,0 +1,37 @@
+#!/bin/bash
+
+PYTHON=""
+function get_python {
+    if [ -z "$PYTHON" ]; then
+        PYTHON=$(which python3)
+        if [ -z "$PYTHON" ]; then
+            PYTHON=$(which python)
+            if [ -z "$PYTHON" ]; then
+                echo "Python or Python3 is required"
+                exit 1
+            fi
+        fi
+    fi
+}
+
+function check_venv {
+    if [ ! -d "venv" ]; then
+    echo "Creating virtual environment"
+        $PYTHON -m venv venv
+        source venv/bin/activate
+        pip install .
+        echo "Dependencies installed"
+        deactivate
+    fi
+}
+
+
+get_python
+check_venv
+source venv/bin/activate
+python dbibackend/dbi.py --help
+
+echo ""
+echo "Now you can use the dbi command"
+
+alias dbi="python $(pwd)/dbibackend/dbi.py"