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AD7779 always returns 0

Question asked by ndomblides on Feb 2, 2017
Latest reply on Feb 3, 2017 by Lluis

Hi,

 

I'm evaluating the AD7779 with a microcontroler using the SPI control mode. 

I have configured the ADC to enable AIN0 to AIN3. The reference is an external reference as defined in figure 98 of the datasheet.

I've around 200 mV in differential and more than 1V to GND on each channel. The ADC is supplied in 3.3V (single supply).

When I'm readbacking the Sigma Delta values, I always have 0x000000. (Received data are 0x00 00 00 00 / 0x10 00 00 00 / 0x20 00 00 00 / 0x30 00 00 00 )

 

Do you have any Idea about the wrong configuration I did ?

 

Here under the value of the internal registers : 

cached_reg_val[CH_DISABLE] : 240 (0xF0)
cached_reg_val[GENERAL_USER_CONFIG_1] : 115 (0x73)
cached_reg_val[GENERAL_USER_CONFIG_2] : 1
cached_reg_val[GENERAL_USER_CONFIG_3] : 209 (0xD1)
cached_reg_val[DOUT_FORMAT] : 192 (0xC0)
cached_reg_val[GPIO_DATA] : 48 (0x30)
cached_reg_val[BUFFER_CONFIG_1] : 56 (0x38)
cached_reg_val[CH4_5_SAT_ERR] : 57 (0x39)
cached_reg_val[CH6_7_SAT_ERR] : 63 (0x3F)
cached_reg_val[CHX_ERR_REG_EN] : 255 (0xFF)
cached_reg_val[GEN_ERR_REG_1] : 0
cached_reg_val[GEN_ERR_REG_1_EN] : 30 (0x1e)
cached_reg_val[GEN_ERR_REG_2] : 0
cached_reg_val[GEN_ERR_REG_2_EN] : 60 (0x3C)
cached_reg_val[STATUS_REG_1] : 0
cached_reg_val[STATUS_REG_2] : 0
cached_reg_val[STATUS_REG_3] : 16 (0x10)
cached_reg_val[SRC_N_MSB] : 8 (0x08)
cached_reg_val[SRC_N_LSB] : 0
cached_reg_val[SRC_IF_MSB] : 0
cached_reg_val[SRC_IF_LSB] : 0
cached_reg_val[SRC_UPDATE] : 0

 

All other registers are equal to 0.

 

Thank you for your Help.

 

Nicolas

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