add examples

RTL00_SDKV35a/example_sources/i2c-shtc1/readme.txt

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+Example Description
+
+This example describes how to use i2c by using mbed api
+
+work with arduino extended board, which has SHTC1 temperature and humidity 
+sensor
+
+Connect 
+  - I2C3 SDA (PB_3) to extended board's SDA 
+  - I2C3 SCL (PB_2) to extended board's SCL 
+  
+
+

RTL00_SDKV35a/example_sources/i2c-shtc1/src/main.c

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+
+#include "device.h"
+#include "PinNames.h"
+
+#include "basic_types.h"
+#include "diag.h" 
+#include "osdep_api.h"
+
+#include "i2c_api.h"
+#include "pinmap.h"
+#include "rtl_lib.h"
+
+#define NO_ERROR        0x00
+#define ACK_ERROR       0x01
+#define CHECKSUM_ERROR  0x02
+#define NULL_ERROR      0x03
+
+#define MBED_I2C_MTR_SDA    PD_4
+#define MBED_I2C_MTR_SCL    PD_5
+
+#define MBED_I2C_SLAVE_ADDR0    0x70
+#define POLYNOMIAL 0x131 // P(x) = x^8 + x^5 + x^4 + 1 = 100110001
+
+
+#define MBED_I2C_BUS_CLK        100000  //hz
+#define I2C_DATA_MAX_LENGTH     16
+
+uint8_t i2cdata_write[I2C_DATA_MAX_LENGTH];
+uint8_t i2cdata_read[I2C_DATA_MAX_LENGTH];
+int i2cdata_read_pos;
+
+volatile i2c_t   i2cmaster;
+
+
+// Sensor Commands
+#define READ_ID              0xEFC8 // command: read ID register
+#define SOFT_RESET           0x805D // soft resetSample Code for SHTC1
+#define MEAS_T_RH_POLLING    0x7866 // meas. read T first, clock stretching disabled
+#define MEAS_T_RH_CLOCKSTR   0x7CA2 // meas. read T first, clock stretching enabled
+#define MEAS_RH_T_POLLING    0x58E0 // meas. read RH first, clock stretching disabled
+#define MEAS_RH_T_CLOCKSTR   0x5C24 // meas. read RH first, clock stretching enabled
+
+
+static int SHTC1_GetID(uint16_t *id);
+static void SHTC1_WriteCommand(uint16_t cmd);
+static int SHTC1_Read2BytesAndCrc(uint16_t *data);
+static int SHTC1_CheckCrc(uint8_t data[], uint8_t nbrOfBytes, uint8_t checksum);
+static float SHTC1_CalcTemperature(uint16_t rawValue);
+static float SHTC1_CalcHumidity(uint16_t rawValue);
+
+
+int SHTC1_Init(uint16_t *pID)
+{
+  int error = NO_ERROR;
+
+  DiagPrintf("SHTC1_Init \r\n");
+
+  i2c_init((i2c_t*)&i2cmaster, MBED_I2C_MTR_SDA ,MBED_I2C_MTR_SCL);
+  i2c_frequency((i2c_t*)&i2cmaster,MBED_I2C_BUS_CLK);
+ 
+  if (pID == NULL ) return NULL_ERROR;
+
+  
+  error = SHTC1_GetID(pID);
+  return error;
+}
+
+static int SHTC1_GetID(uint16_t *id)
+{
+  int error = NO_ERROR;
+  uint8_t bytes[2];
+  uint8_t checksum;
+
+  SHTC1_WriteCommand(READ_ID);  
+
+  i2c_read((i2c_t*)&i2cmaster, MBED_I2C_SLAVE_ADDR0, (char*)&i2cdata_read[0], 3, 1);
+  i2cdata_read_pos = 0;
+  error = SHTC1_Read2BytesAndCrc(id);
+
+  return error;
+}
+
+static int SHTC1_Read2BytesAndCrc(uint16_t *data)
+{
+  int error;
+  int readed;
+  uint8_t bytes[2];
+  uint8_t checksum;
+
+
+  
+  bytes[0] = i2cdata_read[i2cdata_read_pos++];
+  bytes[1] = i2cdata_read[i2cdata_read_pos++];
+  checksum = i2cdata_read[i2cdata_read_pos++];
+
+  error = SHTC1_CheckCrc(bytes, 2, checksum);
+  *data = (bytes[0] << 8) | bytes[1];  
+  
+  return error;
+}
+
+static int SHTC1_CheckCrc(uint8_t data[], uint8_t nbrOfBytes, uint8_t checksum)
+{
+   uint8_t bit; // bit mask
+   uint8_t crc = 0xFF; // calculated checksum
+   uint8_t byteCtr; // byte counter
+
+   // calculates 8-Bit checksum with given polynomial
+   for(byteCtr = 0; byteCtr < nbrOfBytes; byteCtr++)
+   {
+     crc ^= (data[byteCtr]);
+     for(bit = 8; bit > 0; --bit)
+     {
+       if(crc & 0x80) crc = (crc << 1) ^ POLYNOMIAL;
+       else crc = (crc << 1);
+     }
+  }
+
+   // verify checksum
+   if(crc != checksum) return CHECKSUM_ERROR;
+   else return NO_ERROR;
+}
+
+
+static void SHTC1_WriteCommand(uint16_t cmd)
+{
+	int writebytes; 
+
+	i2cdata_write[0] = (uint8_t)(cmd >>8);
+	i2cdata_write[1] = (uint8_t)(cmd&0xFF);
+  	i2c_write((i2c_t*)&i2cmaster, MBED_I2C_SLAVE_ADDR0, &i2cdata_write[0], 2, 1);
+}  
+
+static float SHTC1_CalcTemperature(uint16_t rawValue)
+{
+  return 175.0 * (float)rawValue / 65536.0 - 45.0;
+}
+
+static float SHTC1_CalcHumidity(uint16_t rawValue)
+{
+  return 100.0 * (float)rawValue / 65536.0;
+} 
+
+int SHTC1_GetTempAndHumi(float *temp, float *humi)
+{
+  int error;
+  uint16_t rawValueTemp;
+  uint16_t rawValueHumi;
+  
+  SHTC1_WriteCommand(MEAS_T_RH_CLOCKSTR);  
+
+  //Wire1.requestFrom(I2C_ADR_SHTC1, 6);   
+  i2c_read((i2c_t*)&i2cmaster, MBED_I2C_SLAVE_ADDR0, (char*)&i2cdata_read[0], 6, 1);
+  i2cdata_read_pos = 0;
+  error = NO_ERROR;
+  error |= SHTC1_Read2BytesAndCrc(&rawValueTemp);
+  error |= SHTC1_Read2BytesAndCrc(&rawValueHumi);
+
+  //diag_printf("raw temp=0x%x, raw humidity=0x%x, error=%d\n", 
+  //          rawValueTemp, rawValueHumi, error);
+ 
+  if ( error == NO_ERROR ) {
+    *temp = SHTC1_CalcTemperature(rawValueTemp);
+    *humi = SHTC1_CalcHumidity(rawValueHumi);
+  }
+  
+  return error;
+}
+
+
+void main(void)
+{
+    gpio_t gpio_led;
+	int led_status;
+	int i2clocalcnt;
+	int error;
+	uint16_t shtc1_id;
+	
+	float temperature = 1.123f;
+	float humidity = 2.456f;
+
+
+    DBG_8195A("sleep 10 sec. to wait for UART console\n");
+	RtlMsleepOS(10000);
+	
+
+    DBG_8195A("start i2c example - SHTC1\n");
+
+		
+	error = SHTC1_Init(&shtc1_id);
+	if ( error == NO_ERROR ) {
+	  DiagPrintf("SHTC1 init ok, id=0x%x\r\n", shtc1_id);
+	} else {
+	  DiagPrintf("SHTC1 init FAILED! \r\n");
+	  for(;;);
+	}
+	
+	
+	while(1){
+		error = SHTC1_GetTempAndHumi(&temperature, &humidity);
+		
+		rtl_printf("temp=%f, humidity=%f, error=%d\n", 
+				  temperature, humidity, error);
+		
+		RtlMsleepOS(1000);
+
+	}
+}
+