AD7998 can only read channel 1

I tried the sequential read again with a repeated start set on the FT260 for the 0x70 write and again for the 16 byte read. I then send a stop command. Channel 1 is fine, but the other 7 channels are garbage. 

I add some red arrows to some SDA bits I am not sure what that is. Its at the end of each byte. Maybe part of the ACK. 

Starting from the top with channel 1 down to channel 8 below is what I am getting. several channels are grounded along with channel 1. 

Would be nice to get this resolved. I have tried everything I can think of for the past two days. 

Stupid me! I did not mask out the top bits which are the Channel ID bits. 

Rooky Mistake.

Plus I did not see that the voltage dividers for each channel are different on the schematic. Need better glasses.

All seems to be working now with the repeat start on the FT260

I included my C# working code in case anyone else needs to use the FT260 USB to I2C with the AD7998

I need to play around with the highlighted areas to make sure if I need the extra stop command. The AD7998 can lock up the bus if it does not receive a stop.

private void button6_Click(object sender, EventArgs e)
{

byte[] Reading = new byte[100];

// ################################# AD7998 Setup and Read ADC Voltages#########################################

byte[] VoltageAddressReg = new byte[10];
byte[] CurrentAddressReg = new byte[10];
byte[] WriteByteBuf = new byte[10];
UInt32 numBytesToWrite = 0;
UInt32 numBytesToRead = 0;
UInt32 readLength = 0;
UInt32 writeLength = 0;

int size = Marshal.SizeOf(VoltageAddressReg[0]) * VoltageAddressReg.Length;
IntPtr pnt = Marshal.AllocHGlobal(size);

WriteByteBuf[0] = 0x02; //Register pointer to Configuration Register
WriteByteBuf[1] = 0x0F; // Config Reg High byte--Convert CH8,C7,CH6,CH5
WriteByteBuf[2] = 0xF8; // Config Reg Low byte--Convert CH4,CH3,CH2,CH1, Filer on

numBytesToWrite = 3;
Marshal.Copy(WriteByteBuf, 0, pnt, WriteByteBuf.Length);
Status = FT260_I2CMaster_Write(ft260handle, 0x21, FT260_I2C_FLAG.FT260_I2C_START_AND_STOP, pnt, numBytesToWrite, ref writeLength);

if ((Status != FT260_STATUS.FT260_OK) || (writeLength != numBytesToWrite))
{
SetControls_Error("Error", "Please check hardware and re-start application (AD7998W1)");
return;
}

WriteByteBuf[0] = 0x70; //Register pointer to Conversion Result register, Turn on Mode 2 for all channels

numBytesToWrite = 1;
Marshal.Copy(WriteByteBuf, 0, pnt, WriteByteBuf.Length);
Status = FT260_I2CMaster_Write(ft260handle, 0x21, FT260_I2C_FLAG.FT260_I2C_REPEATED_START, pnt, numBytesToWrite, ref writeLength);

if ((Status != FT260_STATUS.FT260_OK) || (writeLength != numBytesToWrite))
{
SetControls_Error("Error", "Please check hardware and re-start application (AD7998W2)");
return;
}

numBytesToRead = 16;
Status = FT260_I2CMaster_Read(ft260handle, 0x21, FT260_I2C_FLAG.FT260_I2C_START, pnt, numBytesToRead, ref readLength, 5000);

numBytesToWrite = 1;
Status = FT260_I2CMaster_Write(ft260handle, 0x21, FT260_I2C_FLAG.FT260_I2C_STOP, pnt, numBytesToWrite, ref writeLength);

if (Status == FT260_STATUS.FT260_OTHER_ERROR)
{
SetControls_Error("Error", "Please check hardware and re-start application (AD7998R1)");
return;
}

if (Status == FT260_STATUS.FT260_I2C_READ_FAIL)
{
SetControls_Error_AllowReInit("Stopped", "Capture stopped: Click Initialise and the Start to begin again (AD7998R2)");
return;
}

if ((Status != FT260_STATUS.FT260_OK) || (readLength != numBytesToRead))
{
SetControls_Error("Error", "Please check hardware and re-start application (AD7998R3)");
return;
}

Marshal.Copy(pnt, Reading, 0, (int)numBytesToRead);
ushort CH1 = (ushort)(((Reading[0] & 0x0F) * 256) + Reading[1]);
ushort CH2 = (ushort)(((Reading[2] & 0x0F) * 256) + Reading[3]);
ushort CH3 = (ushort)(((Reading[4] & 0x0F) * 256) + Reading[5]);
ushort CH4 = (ushort)(((Reading[6] & 0x0F) * 256) + Reading[7]);
ushort CH5 = (ushort)(((Reading[8] & 0x0F) * 256) + Reading[9]);
ushort CH6 = (ushort)(((Reading[10] & 0x0F) * 256) + Reading[11]);
ushort CH7 = (ushort)(((Reading[12] & 0x0F) * 256) + Reading[13]);
ushort CH8 = (ushort)(((Reading[14] & 0x0F) * 256) + Reading[15]);

labelCH1.Text = CH1.ToString();
labelCH2.Text = CH2.ToString();
labelCH3.Text = CH3.ToString();
labelCH4.Text = CH4.ToString();
labelCH5.Text = CH5.ToString();
labelCH6.Text = CH6.ToString();
labelCH7.Text = CH7.ToString();
labelCH8.Text = CH8.ToString();
}

Hi Gubo ,

Glad you have resolved your issue. Feel free to post another thread if you need further assistance. I will be closing this thread now.

Regards,

JC