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+/*
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+ * app/modules/am2320.c
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+ *
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+ * Copyright (c) 2016 Henk Vergonet <Henk.Vergonet@gmail.com>
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+ *
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+ * This program is free software; you can redistribute it and/or
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+ * modify it under the terms of the GNU General Public License as
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+ * published by the Free Software Foundation; either version 2 of
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+ * the License, or (at your option) any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program; if not, write to the Free Software
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+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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+ */
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+#include "module.h"
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+#include "lauxlib.h"
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+#include "platform.h"
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+#include "lwip/udp.h"
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+#include <errno.h>
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+
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+static const uint32_t am2320_i2c_id = 0;
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+static const uint8_t am2320_i2c_addr = 0xb8 >> 1;
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+
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+static uint16_t crc16(uint8_t *ptr, unsigned int len)
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+{
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+ uint16_t crc =0xFFFF;
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+ uint8_t i;
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+
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+ while(len--) {
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+ crc ^= *ptr++;
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+ for(i=0;i<8;i++) {
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+ if(crc & 0x01) {
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+ crc >>= 1;
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+ crc ^= 0xA001;
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+ } else {
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+ crc >>= 1;
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+ }
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+ }
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+ }
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+ return crc;
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+}
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+
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+/* make sure buf has lenght len+2 in order to accommodate for extra bytes */
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+static int _read(uint32_t id, void *buf, uint8_t len, uint8_t off)
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+{
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+ int i;
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+ uint8_t *b = (uint8_t *)buf;
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+ uint16_t crc;
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+
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+ // step 1: Wake sensor
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+ platform_i2c_send_start(id);
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+ platform_i2c_send_address(id, am2320_i2c_addr, PLATFORM_I2C_DIRECTION_TRANSMITTER);
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+ os_delay_us(800);
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+ platform_i2c_send_stop(id);
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+
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+ // step 2: Send read command
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+ platform_i2c_send_start(id);
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+ platform_i2c_send_address(id, am2320_i2c_addr, PLATFORM_I2C_DIRECTION_TRANSMITTER);
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+ platform_i2c_send_byte(id, 0x03);
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+ platform_i2c_send_byte(id, off);
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+ platform_i2c_send_byte(id, len);
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+ platform_i2c_send_stop(id);
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+
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+ // step 3: Read the data
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+ os_delay_us(1500);
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+ platform_i2c_send_start(id);
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+ platform_i2c_send_address(id, am2320_i2c_addr, PLATFORM_I2C_DIRECTION_RECEIVER);
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+ os_delay_us(30);
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+ for(i=0; i<len+2; i++)
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+ b[i] = platform_i2c_recv_byte(id,1);
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+ crc = platform_i2c_recv_byte(id,1);
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+ crc |= platform_i2c_recv_byte(id,0) << 8;
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+ platform_i2c_send_stop(id);
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+
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+ if(b[0] != 0x3 || b[1] != len)
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+ return -EIO;
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+ if(crc != crc16(b,len+2))
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+ return -EIO;
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+ return 0;
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+}
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+
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+static int am2320_init(lua_State* L)
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+{
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+ uint32_t sda;
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+ uint32_t scl;
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+ int ret;
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+ struct {
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+ uint8_t cmd;
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+ uint8_t len;
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+ uint16_t model;
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+ uint8_t version;
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+ uint32_t id;
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+ } nfo;
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+
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+ if (!lua_isnumber(L, 1) || !lua_isnumber(L, 2)) {
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+ return luaL_error(L, "wrong arg range");
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+ }
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+
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+ sda = luaL_checkinteger(L, 1);
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+ scl = luaL_checkinteger(L, 2);
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+
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+ if (scl == 0 || sda == 0) {
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+ return luaL_error(L, "no i2c for D0");
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+ }
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+
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+ platform_i2c_setup(am2320_i2c_id, sda, scl, PLATFORM_I2C_SPEED_SLOW);
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+
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+ os_delay_us(1500); // give some time to settle things down
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+ ret = _read(am2320_i2c_id, &nfo, sizeof(nfo)-2, 0x08);
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+ if(ret)
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+ return luaL_error(L, "transmission error");
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+
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+ lua_pushinteger(L, ntohs(nfo.model));
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+ lua_pushinteger(L, nfo.version);
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+ lua_pushinteger(L, ntohl(nfo.id));
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+ return 3;
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+}
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+
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+static int am2320_read(lua_State* L)
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+{
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+ int ret;
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+ struct {
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+ uint8_t cmd;
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+ uint8_t len;
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+ uint16_t rh;
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+ uint16_t temp;
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+ } nfo;
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+
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+ ret = _read(am2320_i2c_id, &nfo, sizeof(nfo)-2, 0x00);
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+ if(ret)
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+ return luaL_error(L, "transmission error");
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+
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+ ret = ntohs(nfo.temp);
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+ if(ret & 0x8000)
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+ ret = -(ret & 0x7fff);
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+
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+ lua_pushinteger(L, ntohs(nfo.rh));
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+ lua_pushinteger(L, ret);
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+ return 2;
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+}
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+
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+static const LUA_REG_TYPE am2320_map[] = {
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+ { LSTRKEY( "read" ), LFUNCVAL( am2320_read )},
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+ { LSTRKEY( "init" ), LFUNCVAL( am2320_init )},
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+ { LNILKEY, LNILVAL}
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+};
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+
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+NODEMCU_MODULE(AM2320, "am2320", am2320_map, NULL);
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