From d60cdb1d2e4b9194c78e52070868d4e61a1fb8a6 Mon Sep 17 00:00:00 2001
From: David Thornley <thornley.david@gmail.com>
Date: Thu, 9 Jul 2020 00:11:35 +1000
Subject: [PATCH] Added AM2320 support

Ported raw from 8266 implementation, still using busy-wait for read function
fix whitespace
---
 components/modules/Kconfig  |   6 ++
 components/modules/am2320.c | 139 ++++++++++++++++++++++++++++++++++++
 docs/modules/am2320.md      |  42 +++++++++++
 mkdocs.yml                  |   1 +
 4 files changed, 188 insertions(+)
 create mode 100644 components/modules/am2320.c
 create mode 100644 docs/modules/am2320.md

diff --git a/components/modules/Kconfig b/components/modules/Kconfig
index 574f0bfdd2..68a38c6203 100644
--- a/components/modules/Kconfig
+++ b/components/modules/Kconfig
@@ -54,6 +54,12 @@ config LUA_MODULE_ADC
       Includes the adc module. This module provides access to the
       adc1 hardware.
 
+config LUA_MODULE_AM2320
+  bool "AM2320 module"
+  default "n"
+  help
+      Support for AM2320 temp/humidity sensor
+
 config LUA_MODULE_BIT
   bool "Bit module"
   default "n"
diff --git a/components/modules/am2320.c b/components/modules/am2320.c
new file mode 100644
index 0000000000..9b9f3f9064
--- /dev/null
+++ b/components/modules/am2320.c
@@ -0,0 +1,139 @@
+/*
+ * app/modules/am2320.c
+ *
+ * Copyright (c) 2016 Henk Vergonet <Henk.Vergonet@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#include "module.h"
+#include "lauxlib.h"
+#include "platform.h"
+#include "lwip/udp.h"
+#include <errno.h>
+
+static const uint32_t am2320_i2c_id = 0;
+static const uint8_t am2320_i2c_addr = 0xb8 >> 1;
+
+static uint16_t crc16(uint8_t *ptr, unsigned int len)
+{
+  uint16_t	crc =0xFFFF;
+  uint8_t	i;
+
+  while(len--) {
+    crc ^= *ptr++;
+    for(i=0;i<8;i++) {
+      if(crc & 0x01) {
+        crc >>= 1;
+        crc ^= 0xA001;
+	    } else {
+		    crc >>= 1;
+	    }
+    }
+  }
+  return crc;
+}
+
+/* make sure buf has lenght len+2 in order to accommodate for extra bytes */
+static int _read(uint32_t id, void *buf, uint8_t len, uint8_t off)
+{
+  int i;
+  uint8_t *b = (uint8_t *)buf;
+  uint16_t crc;
+
+  // step 1: Wake sensor
+  platform_i2c_send_start(id);
+  platform_i2c_send_address(id, am2320_i2c_addr, PLATFORM_I2C_DIRECTION_TRANSMITTER, 1);
+  ets_delay_us(800);
+  platform_i2c_send_stop(id);
+
+  // step 2: Send read command
+  platform_i2c_send_start(id);
+  platform_i2c_send_address(id, am2320_i2c_addr, PLATFORM_I2C_DIRECTION_TRANSMITTER, 1);
+  platform_i2c_send_byte(id, 0x03, 1);
+  platform_i2c_send_byte(id, off, 1);
+  platform_i2c_send_byte(id, len, 1);
+  platform_i2c_send_stop(id);
+
+  // step 3: Read the data
+  ets_delay_us(1500);
+  platform_i2c_send_start(id);
+  platform_i2c_send_address(id, am2320_i2c_addr, PLATFORM_I2C_DIRECTION_RECEIVER, 1);
+  ets_delay_us(30);
+  for(i=0; i<len+2; i++)
+    b[i] = platform_i2c_recv_byte(id,1);
+  crc  = platform_i2c_recv_byte(id,1);
+  crc |= platform_i2c_recv_byte(id,0) << 8;
+  platform_i2c_send_stop(id);
+
+  if(b[0] != 0x3 || b[1] != len)
+    return -EIO;
+  if(crc != crc16(b,len+2))
+    return -EIO;
+
+  return 0;
+}
+
+static int am2320_setup(lua_State* L)
+{
+  int ret;
+  struct {
+    uint8_t  cmd;
+    uint8_t  len;
+    uint16_t model;
+    uint8_t	 version;
+    uint32_t id;
+  } nfo;
+
+  ets_delay_us(1500); // give some time to settle things down
+  ret = _read(am2320_i2c_id, &nfo, sizeof(nfo)-2, 0x08);
+  if(ret)
+    return luaL_error(L, "transmission error");
+
+  lua_pushinteger(L, ntohs(nfo.model));
+  lua_pushinteger(L, nfo.version);
+  lua_pushinteger(L, ntohl(nfo.id));
+  return 3;
+}
+
+static int am2320_read(lua_State* L)
+{
+  int ret;
+  struct {
+    uint8_t  cmd;
+    uint8_t  len;
+    uint16_t rh;
+    uint16_t temp;
+  } nfo;
+
+  ret = _read(am2320_i2c_id, &nfo, sizeof(nfo)-2, 0x00);
+  if(ret)
+    return luaL_error(L, "transmission error");
+
+  ret = ntohs(nfo.temp);
+  if(ret & 0x8000)
+    ret = -(ret & 0x7fff);
+
+  lua_pushinteger(L, ntohs(nfo.rh));
+  lua_pushinteger(L, ret);
+  return 2;
+}
+
+LROT_BEGIN(am2320)
+  LROT_FUNCENTRY( read, am2320_read )
+  LROT_FUNCENTRY( setup, am2320_setup )
+LROT_END(am2320, NULL, 0)
+
+
+NODEMCU_MODULE(AM2320, "am2320", am2320, NULL);
diff --git a/docs/modules/am2320.md b/docs/modules/am2320.md
new file mode 100644
index 0000000000..164460d5c9
--- /dev/null
+++ b/docs/modules/am2320.md
@@ -0,0 +1,42 @@
+# AM2320 Module
+| Since  | Origin / Contributor  | Maintainer  | Source  |
+| :----- | :-------------------- | :---------- | :------ |
+| 2016-02-14 | [Henk Vergonet](https://github.com/hvegh) | [Henk Vergonet](https://github.com/hvegh) | [am2320.c](../../components/modules/am2320.c)|
+
+This module provides access to the [AM2320](https://akizukidenshi.com/download/ds/aosong/AM2320.pdf) humidity and temperature sensor, using the i2c interface.
+
+## am2320.read()
+Samples the sensor and returns the relative humidity in % and temperature in celsius, as an integer multiplied with 10.
+
+#### Syntax
+`am2320.read()`
+
+#### Returns
+- `relative humidity` percentage multiplied with 10 (integer)
+- `temperature` in celcius multiplied with 10 (integer)
+
+#### Example
+```lua
+sda, scl = 1, 2
+i2c.setup(0, sda, scl, i2c.SLOW) -- call i2c.setup() only once
+am2320.setup()
+rh, t = am2320.read()
+print(string.format("RH: %s%%", rh / 10))
+print(string.format("Temperature: %s degrees C", t / 10))
+```
+
+## am2320.setup()
+Initializes the module. Returns model, version, serial but is seams these where all zero on my model.
+
+#### Syntax
+`model, version, serial = am2320.setup()`
+
+#### Parameters
+None
+
+#### Returns
+- `model`  16 bits number of model
+- `version`  8 bits version number
+- `serial`  32 bits serial number
+
+   Note: I have only observed values of 0 for all of these, maybe other sensors return more sensible readings.
diff --git a/mkdocs.yml b/mkdocs.yml
index f8e813e2cb..1059ef3ea3 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -34,6 +34,7 @@ pages:
     - Filesystem on SD card: 'sdcard.md'
 - C Modules:
     - 'adc':          'modules/adc.md'
+    - 'am2320':       'modules/am2320.md'
     - 'bit':          'modules/bit.md'
     - 'bthci':        'modules/bthci.md'
     - 'can':          'modules/can.md'