ads1115 differential readings

[simon]

hey

so i'm using the ads1115 example that is provided with pi4j but i'm having a hard time figuring out if and how i can use the differential readings function off the ads1115 chip from the provided code is this possible?

if not is there any good way that i myself can implement this functionality with out reprogramming/remaking the entire communication class to the ads1115?  

[Robert Savage]

Hi Simon,

Its been a long time since I have looked at that code or that chip.  But I was remembering that only singled ended was implemented and no config support for differential.

I just took a peek and yes, only single ended is implemented.

See: https://github.com/Pi4J/pi4j/blob/master/pi4j-gpio-extension/src/main/java/com/pi4j/gpio/extension/ads/ADS1x15GpioProvider.java#L314

I would think this class could be adapted to support differential readings.  Perhaps some optional configuration settings passed in as part of the constructor rather than the static configuration that exists now.   I know the chip only supports two inputs in differential mode so something may need to be done to map the correct virtual pins to the appropriate chip registers. 

Thanks, 

-Robert

[Sachin Singh]

unsigned char ADS1115_Read_MiliVolts(float* MiliVolt)  Read 2 Bytes

{

float MVolt = 0 ;

unsigned char Data[] = {0x00 , 0x00};

if( I2C_Read(I2C1 , Data , 2 , AddresDS1115 , 0x00 , 1 ) )  0x00 = Select Data Reg

return 1 ;  Timed Out

      If ADC is NOT connected to voltage , Erratic Readings will Come

  But once voltage is aplied to channel , erratic reading will go away

Data[0] &= 0x7F ;  Make Sign bit of MSByte = 0

MVolt = 0.0625f * (float)(( Data[0] << 8 ) | Data[1] ) ;  Data[0] = MSByte

if( MVolt <= 2000 )  Apply Limits

*MiliVolt = MVolt;

     Else Last value of MiliVolt

return 0 ;  No Time Out

}

unsigned char ADS1115_SetUP(unsigned char chanel)

{

ADS1115_RDY_INTR();  Setup STM32 Interrupt for READY

Alert Interrupt Setup - Gives 8 uSec Pulse  - Use Pull Up Resistor

MSBit Low Threshold = 0          MSBit High Threshold = 1

unsigned char TimeOut = 0x00 ;

unsigned char Threshold[] = {0x00 , 0x00};

TimeOut |= I2C_Write(I2C1 , Threshold, 2, AddresDS1115 ,0x02 , 1);  Low Threshold

Threshold[0] = 0x80 ;

TimeOut |= I2C_Write(I2C1 , Threshold, 2, AddresDS1115 ,0x03 , 1);  High Threshold

Config Reg Setup

unsigned char ConfigReg[] = {0x34 , 0xE3};  C3 = 475 SPS , E3 = 860 SPS

if (chanel == 0)

*ConfigReg = 0x04 ;

return I2C_Write(I2C1 , ConfigReg, 2, AddresDS1115 ,0x01 , 1);

0x01 = Config Reg  , 1 = Config Reg 1 byte address

0x34 / 0x04 Goes to MSByte and 0xC3 goes to LSByte of ConfigReg

}

unsigned char ADS1115_Set_Chanel(unsigned char chanel)

 Set Chanel = Mux , Full Scale = PGA 2.048 ,  Data Rate = 475 SPS

{

Timer7SetupMicro();  setup timer in micro sec mode to use in WhileTimed

WhileTimed( I2C_GetFlagStatus(I2C1 , I2C_FLAG_BUSY)   ) ;

I2C_GenerateSTART(I2C1 , ENABLE);

WhileTimed( ! I2C_CheckEvent(I2C1 , I2C_EVENT_MASTER_MODE_SELECT)  ) ;

I2C_Send7bitAddress(I2C1 , AddresDS1115 << 1  ,I2C_Direction_Transmitter);

WhileTimed( ! I2C_CheckEvent(I2C1 ,I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED) ) ;

Device has returned Ack => Address Ok , Device Ok

I2C_SendData(I2C1 , 0x01 );  Select Config Reg = write 1st byte

WhileTimed( ! I2C_GetFlagStatus(I2C1 , I2C_FLAG_BTF)  ) ; wait on BTF

if(chanel)

I2C_SendData(I2C1 , 0x34 ) ;  MSB Config Register

else                               Volt = 2.048  Continous

I2C_SendData(I2C1 , 0x04 ) ;  MSB Config Reg

WhileTimed( ! I2C_GetFlagStatus(I2C1 , I2C_FLAG_BTF)  ) ; wait on BTF

I2C_SendData(I2C1 , 0xC3 ) ;  Sample Per Sec

WhileTimed( ! I2C_GetFlagStatus(I2C1 , I2C_FLAG_BTF)  ) ; wait on BTF

I2C_GenerateSTOP(I2C1 , ENABLE);

WhileTimed( I2C_GetFlagStatus(I2C1 , I2C_FLAG_STOPF) );

/

TIM_Cmd(TIM7, DISABLE);  Desable WhileTimed Timer 7

return 0;  No Time Out

ErrorTimeOut :

TIM_Cmd(TIM7, DISABLE);

return 1 ;  Yes Timed Out

}

unsigned char ADS1115_Read_MiliVolts(unsigned char chanel , float *MiLVolts)  Read 2 Bytes

{

ADS1115_Set_Chanel(chanel) ;

Delay( 0 , 100 );

Timer7SetupMicro();  setup timer in micro sec mode to use in WhileTimed

unsigned char MSB = 0 , LSB = 0 ;

WhileTimed( I2C_GetFlagStatus(I2C1 , I2C_FLAG_BUSY) ) ;

I2C_GenerateSTART(I2C1 , ENABLE);

WhileTimed( ! I2C_CheckEvent(I2C1 , I2C_EVENT_MASTER_MODE_SELECT)  ) ;

I2C_Send7bitAddress(I2C1 , AddresDS1115 << 1  ,I2C_Direction_Transmitter);

while( ! I2C_CheckEvent(I2C1 ,I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED) ) ;

Ack From Slave

WhileTimed (!(I2C_CheckEvent (I2C1, I2C_EVENT_MASTER_TRANSMITTER_MODE_SELECTED & ~((uint32_t) I2C_SR1_ADDR)))) ;

I2C_SendData(I2C1 , 0x00 );  Select Data Reg

WhileTimed( ! I2C_GetFlagStatus(I2C1 , I2C_FLAG_BTF)  ) ; wait on BTF

I2C_GenerateSTOP(I2C1 , ENABLE);

WhileTimed( I2C_GetFlagStatus(I2C1 , I2C_FLAG_STOPF) );

Pointer at data reg set , Start Reading 2 bytes

I2C_AcknowledgeConfig(I2C1 , ENABLE); Enable Ack

I2C_NACKPositionConfig(I2C1 , I2C_NACKPosition_Current);  clear POS flag

Last Communication Complete , New Comms To Be Started

I2C_GenerateSTART(I2C1 , ENABLE);  Start  Bit

WhileTimed (! I2C_CheckEvent(I2C1 , I2C_EVENT_MASTER_MODE_SELECT));  wait for EV5

I2C_Send7bitAddress(I2C1 , AddresDS1115 << 1 , I2C_Direction_Receiver);  Send Address

WhileTimed (! I2C_GetFlagStatus(I2C1 , I2C_FLAG_ADDR)); EV6

I2C_NACKPositionConfig(I2C1 , I2C_NACKPosition_Next); Set POS flag

EV6_1 --> must be atomic and in this order

__disable_irq ();

(void) I2C1 ->SR2;                       Clear ADDR flag

I2C_AcknowledgeConfig(I2C1 , DISABLE);   Clear Ack bit

__enable_irq ();

EV7_3 -- Wait for BTF , program stop , read data twice

WhileTimed (! I2C_GetFlagStatus(I2C1 , I2C_FLAG_BTF));

__disable_irq ();

I2C_GenerateSTOP(I2C1 ,ENABLE);

MSB = I2C1 ->DR;          MSB First

__enable_irq ();

LSB = I2C1 ->DR;

WhileTimed(I2C_GetFlagStatus(I2C1 , I2C_FLAG_STOPF)); Wait for stop Flag

return (( MSB << 8 ) | LSB)  ;

*MiLVolts =  (float)( 0.0625f * (float)(( MSB << 8 ) | LSB ) );

/

TIM_Cmd(TIM7, DISABLE);  Desable WhileTimed Timer 7

return 0;  No Time Out

ErrorTimeOut :

TIM_Cmd(TIM7, DISABLE);

return 1 ;  Yes Timed Out

}

void I2C_Start(void)  I2C1   PB6 = SCL        PB7 = SDA

{

GPIO_InitTypeDef GPIO_InitStructure;

I2C_InitTypeDef I2C_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB , ENABLE);

GPIO_StructInit (& GPIO_InitStructure);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1 , ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_10MHz ;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_OD;  Out Open Drain

GPIO_Init(GPIOB , &GPIO_InitStructure);

I2C1 Reset = Peripheral Reset Register

RCC_APB1PeriphResetCmd(RCC_APB1Periph_I2C1 , ENABLE);

RCC_APB1PeriphResetCmd(RCC_APB1Periph_I2C1 , DISABLE);

Configure I2C1

I2C_StructInit (& I2C_InitStructure);

I2C_InitStructure.I2C_Mode = I2C_Mode_I2C;

I2C_InitStructure.I2C_DutyCycle = I2C_DutyCycle_2;

I2C_InitStructure.I2C_OwnAddress1 = 0 ;

I2C_InitStructure.I2C_Ack = I2C_Ack_Enable;

I2C_InitStructure.I2C_AcknowledgedAddress = I2C_AcknowledgedAddress_7bit;

I2C_InitStructure.I2C_ClockSpeed = 100000;  100 K Hz - 400 K Hz

I2C_Init(I2C1 , &I2C_InitStructure);

I2C_Cmd(I2C1 , ENABLE);

}

void ADS1115_RDY_INTR(void)

{

GPIO Config

RCC->APB2ENR |= (1<<3) | (1<<0) ;  AFIO is must for EXT  + PB

GPIO_InitTypeDef GPIO_InitStruct;

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IPU;  Weak Pull Up

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_0 ;  PB0

GPIO_InitStruct.GPIO_Speed = GPIO_Speed_10MHz;

GPIO_Init(GPIOC, &GPIO_InitStruct);

EXT Line Config

EXTI_InitTypeDef EXTI_InitStruct;

GPIO_EXTILineConfig(GPIO_PortSourceGPIOB, GPIO_PinSource0);  PB0

EXTI_InitStruct.EXTI_Line = EXTI_Line0 ;  EXTI_Line0

EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt;

EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Rising;

EXTI_InitStruct.EXTI_LineCmd = ENABLE;

EXTI_Init(&EXTI_InitStruct);

NVIC Config

NVIC_InitTypeDef NVIC_InitStruct;

NVIC_InitStruct.NVIC_IRQChannel = EXTI0_IRQn;  EXTI0_IRQn = EXTI_Line0 = P - ABCD - 0

NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0x0F;  lowest priority

NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0x0F;  lowest subpriority

NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStruct);

       NVIC_EnableIRQ(EXTI0_IRQn);

}