From 7428042d6fcc97ccb13db1876b60a961af15d610 Mon Sep 17 00:00:00 2001
From: Evgeny Zinoviev <me@ch1p.io>
Date: Tue, 3 Aug 2021 00:43:06 +0300
Subject: initial

---
 README.md               | 10 +++++++
 si7021d                 | 73 +++++++++++++++++++++++++++++++++++++++++++++++++
 systemd/si7021d.service | 10 +++++++
 3 files changed, 93 insertions(+)
 create mode 100644 README.md
 create mode 100644 si7021d
 create mode 100644 systemd/si7021d.service

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..aa463e4
--- /dev/null
+++ b/README.md
@@ -0,0 +1,10 @@
+# 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
\ No newline at end of file
diff --git a/si7021d b/si7021d
new file mode 100644
index 0000000..77b3970
--- /dev/null
+++ b/si7021d
@@ -0,0 +1,73 @@
+#!/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...')
diff --git a/systemd/si7021d.service b/systemd/si7021d.service
new file mode 100644
index 0000000..8537ca4
--- /dev/null
+++ b/systemd/si7021d.service
@@ -0,0 +1,10 @@
+[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
-- 
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