initial

README.md

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+# si7021d
+
+A Linux daemon that reads and returns data from a Si-7021 sensor. Written on Python.
+
+It starts TCP server, accepts command `read` and returns JSON with sensor readings. 
+You can send as many `read` commands during one connection as you want.
+
+## License
+
+MIT

si7021d

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+#!/usr/bin/env python3
+import smbus
+import argparse
+import asyncio
+import json
+import logging
+
+
+logger = logging.getLogger(__name__)
+bus = None
+lock = asyncio.Lock()
+
+
+async def si7021_read():
+    async with lock:
+        await asyncio.sleep(0.01)
+
+        # these are still blocking... meh
+        raw = bus.read_i2c_block_data(0x40, 0xE3, 2)
+        temp = 175.72 * (raw[0] << 8 | raw[1]) / 65536.0 - 46.85
+
+        raw = bus.read_i2c_block_data(0x40, 0xE5, 2)
+        rh = 125.0 * (raw[0] << 8 | raw[1]) / 65536.0 - 6.0
+
+        return rh, temp
+
+
+async def handle_client(reader, writer):
+    request = None
+    while request != 'quit':
+        try:
+            request = await reader.read(255)
+            if request == b'\x04':
+                break
+            request = request.decode('utf-8').strip()
+        except Exception:
+            break
+
+        if request == 'read':
+            rh, temp = await si7021_read()
+            data = dict(humidity=rh, temp=temp)
+        else:
+            data = dict(error='invalid request')
+
+        writer.write((json.dumps(data) + '\r\n').encode('utf-8'))
+        await writer.drain()
+
+    writer.close()
+
+
+async def run_server(host, port):
+    server = await asyncio.start_server(handle_client, host, port)
+    async with server:
+        logger.info('Server started.')
+        await server.serve_forever()
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--host', type=str, default='127.0.0.1')
+    parser.add_argument('--port', type=int, default=8306)
+    parser.add_argument('--bus', type=int, default=0,
+                        help='Bus number (X for /dev/i2c-X)')
+
+    args = parser.parse_args()
+    logging.basicConfig(level=logging.INFO)
+
+    bus = smbus.SMBus(args.bus)
+
+    try:
+        asyncio.run(run_server(args.host, args.port))
+    except KeyboardInterrupt:
+        logging.info('Exiting...')

systemd/si7021d.service

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+[Unit]
+Description=si7021 daemon
+After=network-online.target
+
+[Service]
+Restart=on-failure
+ExecStart=/usr/local/bin/si7021d --bus 0 --host 0.0.0.0
+
+[Install]
+WantedBy=multi-user.target