AD7190 and AD7192 Not respond when input voltage is negative(change polarity from + to- ) in Bipolar mode

AD719x Schematic

Loa cell

$regfile = "m128def.dat"
$crystal = 11059200
$hwstack = 128
$swstack = 128
$framesize = 128
'*******************************************************************************
$lib "glcdKS108.lbx"
$lib "glcdsed.lbx"
Config Graphlcd = 128 * 64sed , Dataport = Portc , Controlport = Porta , Ce = 7 , Ce2 = 3 , Cd = 6 , Rd = 4 , Reset = 2 , Enable = 5

'-----------------------Pins alias -----------------------------

Config Spi = Hard , Interrupt = Off , Data Order = Msb , Master = Yes , _
Polarity = Low , Phase = 0 , Clockrate = 128 , Noss = 0

Spiinit
'******************************************************************8
Data_ready Alias Pinb.3

Set Portb.3
C_s Alias Portd.7
Sync Alias Portb.4

Buz Alias Portg.4


Led1 Alias Porte.0
Led2 Alias Porte.1

Config Led1 = Output
Config Led2 = Output

Config Data_ready = Input
Config Sync = Output
Config C_s = Output
Config Buz = Output

Dim Ad_data(5) As Byte
Dim Data_t(5) As Dword

Dim D(4) As Byte
Dim Reset_reg As Byte
Dim Reg As Byte
Dim cnt As Byte
Dim Mode_reg As Byte
Dim COM_WRITE_CONFIG_REG_CMD As Byte
Dim COM_WRITE_MODE_REG_CMD As Byte
Dim COM_WRITE_GPCON_RED_CMD As Byte
Dim COM_READ_CONFIG_REG_CMD As Byte
Dim COM_READ_STATUS_REG_CMD As Byte
Dim COM_READ_MODE_REG_CMD As Byte
Dim COM_READ_DATA_REG_CMD As Byte
Dim COM_READ_GPCON_REG_CMD As Byte
Dim COM_READ_ID_REG_CMD As Byte
Dim COM_READ_OFFSET_REG_CMD As Byte
Dim COM_READ_FULL_SCALE_REG_CMD As Byte
Dim FS_100_HZ As Byte
Dim FS_1200_HZ As Byte
Dim FS_960_HZ As Byte
Dim FS_2400_HZ As Byte
Dim CONFIG_REG_CMD_MSB As Byte
Dim CONFIG_REG_CMD_MID As Byte
Dim CONFIG_REG_CMD_LSB As Byte
Dim MODE_REG_CMD_MSB As Byte
Dim MODE_REG_CMD_MID As Byte
Dim MODE_REG_CMD_LSB As Byte
Dim COMM_REG_CREAD As Byte

Dim Data_reg As word
Dim Cur As Word

' Commands to write to specific registers
COM_WRITE_CONFIG_REG_CMD = &H10
COM_WRITE_MODE_REG_CMD = &H08
COM_WRITE_GPCON_RED_CMD = &H28
' Commands to read from specific registers
COM_READ_CONFIG_REG_CMD =  &H50
COM_READ_STATUS_REG_CMD = &H40
COM_READ_MODE_REG_CMD = &H48
Com_read_data_reg_cmd = &H58
Com_read_gpcon_reg_cmd = &H68
COM_READ_ID_REG_CMD = &H60
COM_READ_OFFSET_REG_CMD =  &H70
Com_read_full_scale_reg_cmd = &H78
' Sampling Rates
FS_100_HZ =  &H30
Fs_1200_hz = &H04
Fs_960_hz = &H05
Fs_2400_hz = &H02

'Register settings commands for Configuration Register
Config_reg_cmd_msb = &H00
Config_reg_cmd_mid = &H01

'May have to change Gain depending on input signal voltage
'See Table 19 in AD7190 datasheet for more information
Config_reg_cmd_lsb = &H00

' Register settings commands for Mode Register
Mode_reg_cmd_msb = &H08
Mode_reg_cmd_mid = &H00
Mode_reg_cmd_lsb = Fs_100_hz

' Read the data register continously and place the data on DOUT
COMM_REG_CREAD = &H5C

'-----------------------------------------------------------------
Setfont Font8x8
Set Led1
Set Led2
'************************ Sendig Configurations Data To Registers ************************
Ad7190:

Set C_s
Set Sync

Cls

C_s = 0 : Waitms 2
Reset_reg = &HFF

For Cnt = 0 To 5
Spiout Reset_reg , 1
Next

Wait 1                                                      'wait 1 second

'AD7190_configure
Spiout COM_WRITE_CONFIG_REG_CMD , 1
Spiout CONFIG_REG_CMD_MSB , 1
Spiout CONFIG_REG_CMD_MID , 1
Spiout CONFIG_REG_CMD_LSB , 1
 Waitus 10
'AD7190_mode
Spiout Com_write_mode_reg_cmd , 1
Spiout Mode_reg_cmd_msb , 1
Spiout Mode_reg_cmd_mid , 1
Spiout MODE_REG_CMD_LSB , 1
                                             'fs
Waitms 1
'*****************************************************************************************

Do



      Reg = Com_read_data_reg_cmd : Spiout Reg , 1

      Bitwait Data_ready , Reset


      Spiin Ad_data , 3

      Data_t(1) = Ad_data(1) * 65535
      Data_t(2) = Ad_data(2) * 255
      Data_t(2) = Data_t(1) + Data_t(2)

      Data_t(2) = Data_t(2) + Ad_data(3)


      Lcdat 7 , 1 , "d:" ; Data_t(2) ; "       "

      Waitms 200

Loop


$include "Font8x8.font"

Hi AbarNic ,

I see that your comments have been verified. Have you resolved your issue?

Regards,

JC

Hi Dear JCCillion

thank you for reply

No, unfortunately it has not been resolved yet.
Thank you for helping to solve this problem.

Hi AbarNic ,

For additional info, when you say that the AD719x is not responding on negative input, what is the output code of the ADC?

RAdante  will be supporting you in your queries.

Regards,

JC

I have used S type load cell
When the direction of the force is downward, everything is fine, but when the direction of the force is upward, as soon as the polarity of the output voltage of the load cell changes, the AD7190-92 Not responding.
This happens when I use bipolar mode, but when I use unipolar mode, everything is ok , but that doesn't help me, because I can't read the negative voltage (pullup force).
I need to use bipolar mode to read pullup force.

Thanks to anyone who can help me solve this problem.

Hi Dear JC 

the Data_ready pin go high and stay High.

Hi AbarNic ,

Regarding your Data_ready pin on not going low, could you please try referring to number 11 of this FAQ: (+) Digital Interface FAQ - Sigma Delta ADC - Q&A - Precision ADCs - EngineerZone (analog.com) and see if it solves your problem? If not, kindly let us now as we will try on a different approach in solving your issue. 

Thanks and regards,

Rod

Hi Rod

Thank you

No matter what I do, as soon as the polarity of the input voltage (AIN1 AIN2 or AIN3 AIN4)becomes negative (in bipolar mode) the AD7190/92 stops working. Even when the IC is turned on for the first time, if the polarity of the input voltage is negative, the IC will not work.

Regards

Mori