--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Small_CPU/Src/externalInterface.c	Thu Nov 12 19:46:03 2020 +0100
@@ -0,0 +1,161 @@
+/**
+  ******************************************************************************
+  * @file    externalInterface.c
+  * @author  heinrichs weikamp gmbh
+  * @version V0.0.1
+  * @date    07-Nov-2020
+  * @brief   Interface functionality to proceed external analog signal via i2c connection
+  *
+  @verbatim
+  ==============================================================================
+                ##### stm32f4xx_hal_i2c.c modification #####
+  ==============================================================================
+	The LTC2942 requires an repeated start condition without stop condition
+	for data reception.
+
+  @endverbatim
+  ******************************************************************************
+  * @attention
+  *
+  * <h2><center>&copy; COPYRIGHT(c) 2014 heinrichs weikamp</center></h2>
+  *
+  ******************************************************************************
+  */
+/* Includes ------------------------------------------------------------------*/
+
+#include <math.h>
+#include "i2c.h"
+#include "externalInterface.h"
+#include "scheduler.h"
+
+extern SGlobal global;
+
+#define ADC_ANSWER_LENGTH	(5u)		/* 3424 will provide addr + 4 data bytes */
+#define ADC_TIMEOUT			(10u)		/* conversion stuck for unknown reason => restart */
+#define ADC_REF_VOLTAGE_MV	(2048.0f)	/* reference voltage of MPC3424*/
+
+#define ADC_START_CONVERSION		(0x80)
+#define ADC_GAIN_4					(0x02)
+#define ADC_GAIN_4_VALUE			(4.0f)
+#define ADC_GAIN_8					(0x03)
+#define ADC_GAIN_8_VALUE			(8.0f)
+#define ADC_RESOLUTION_16BIT		(0x08)
+#define ADC_RESOLUTION_16BIT_VALUE	(16u)
+#define ADC_RESOLUTION_18BIT		(0x0C)
+#define ADC_RESOLUTION_18BIT_VALUE	(18u)
+
+#define ANSWER_CONFBYTE_INDEX		(4u)
+
+static uint8_t activeChannel = 0;			/* channel which is in request */
+static uint8_t recBuf[ADC_ANSWER_LENGTH];
+static uint8_t timeoutCnt = 0;
+static uint8_t externalInterfacePresent = 0;
+
+float externalChannel_mV[MAX_ADC_CHANNEL];
+
+
+void externalInterface_Init(void)
+{
+	activeChannel = 0;
+	timeoutCnt = 0;
+	externalInterfacePresent = 0;
+	if(externalInterface_StartConversion(activeChannel) == HAL_OK)
+	{
+		externalInterfacePresent = 1;
+		global.deviceDataSendToMaster.hw_Info.extADC = 1;
+	}
+}
+
+
+uint8_t externalInterface_StartConversion(uint8_t channel)
+{
+	uint8_t retval = 0;
+	uint8_t confByte = 0;
+
+	if(channel < MAX_ADC_CHANNEL)
+	{
+		confByte = ADC_START_CONVERSION | ADC_RESOLUTION_16BIT | ADC_GAIN_8;
+		confByte |= channel << 5;
+		retval = I2C_Master_Transmit(DEVICE_EXTERNAL_ADC, &confByte, 1);
+	}
+	return retval;
+}
+
+/* Check if conversion is done and trigger measurement of next channel */
+uint8_t externalInterface_ReadAndSwitch()
+{
+	uint8_t retval = EXTERNAL_ADC_NO_DATA;
+
+	if(externalInterfacePresent)
+	{
+		if(I2C_Master_Receive(DEVICE_EXTERNAL_ADC, recBuf, ADC_ANSWER_LENGTH) == HAL_OK)
+		{
+			if((recBuf[ANSWER_CONFBYTE_INDEX] & ADC_START_CONVERSION) == 0)		/* !ready set => received data contains new value */
+			{
+				retval = activeChannel;										/* return channel number providing new data */
+				activeChannel++;
+				if(activeChannel == MAX_ADC_CHANNEL)
+				{
+					activeChannel = 0;
+				}
+				externalInterface_StartConversion(activeChannel);
+				timeoutCnt = 0;
+			}
+			else
+			{
+				if(timeoutCnt++ >= ADC_TIMEOUT)
+				{
+					externalInterface_StartConversion(activeChannel);
+					timeoutCnt = 0;
+				}
+			}
+		}
+	}
+	return retval;
+}
+float externalInterface_CalculateADCValue(uint8_t channel)
+{
+	int32_t rawvalue = 0;
+	float retValue = 0.0;
+	if(channel < MAX_ADC_CHANNEL)
+	{
+
+		rawvalue = ((recBuf[0] << 16) | (recBuf[1] << 8) | (recBuf[2]));
+
+		switch(recBuf[3] & 0x0C)			/* confbyte => Resolution bits*/
+		{
+			case ADC_RESOLUTION_16BIT:		rawvalue = rawvalue >> 8;										/* only 2 databytes received shift out confbyte*/
+											if(rawvalue & (0x1 << (ADC_RESOLUTION_16BIT_VALUE-1)))			/* MSB set => negative number */
+											{
+												rawvalue |= 0xFFFF0000; 	/* set MSB for int32 */
+											}
+											else
+											{
+												rawvalue &= 0x0000FFFF;
+											}
+											externalChannel_mV[channel] = ADC_REF_VOLTAGE_MV * 2.0 / (float) pow(2,ADC_RESOLUTION_16BIT_VALUE);	/* calculate bit resolution */
+				break;
+			case ADC_RESOLUTION_18BIT:		if(rawvalue & (0x1 << (ADC_RESOLUTION_18BIT_VALUE-1)))			/* MSB set => negative number */
+											{
+												rawvalue |= 0xFFFE0000; 	/* set MSB for int32 */
+											}
+											externalChannel_mV[channel] = ADC_REF_VOLTAGE_MV * 2.0 / (float) pow(2,ADC_RESOLUTION_18BIT_VALUE);	/* calculate bit resolution */
+							break;
+			default: rawvalue = 0;
+				break;
+		}
+		externalChannel_mV[channel] = externalChannel_mV[channel] * rawvalue / ADC_GAIN_8_VALUE;
+		retValue = externalChannel_mV[channel];
+	}
+	return retValue;
+}
+float getExternalInterfaceChannel(uint8_t channel)
+{
+	float retval = 0;
+
+	if(channel < MAX_ADC_CHANNEL)
+	{
+		retval = externalChannel_mV[channel];
+	}
+	return retval;
+}