ADS1148: fail for spi communication

Piero,


There is very little in the schematic that shows what might be happening in the SPI communication. However, there are many things that you can do for debugging this problem.

First, when you have this problem, do you get no communication? or do you get errors in communication? If you are able to get some communications with errors, what errors are you getting? Is the data incorrect? Do you miss commands? If you have the data, it would be important to see it.

Are digital ground and analog ground should be connected. Are R246 or R247 installed? Is the microcontroller on the same ground and running on the same digital supply? Analog and digital supplies cannot be isolated in this device. Make sure they have a direct connection. The same goes with the microcontroller. The two must match supplies to have a good digital connection.

You will also need to verify the digital communication with an oscilloscope or logic analyzer. Using an oscilloscope, make sure the scope ground is connected to the digital ground, and that the scope lead is connected to the ADS1148 side for DIN, SCLK, DOUT and /CS (and /DRDY if you have logic analyzer with more channels).

You must also verify timing requirements and switching characteristics. Tables from sections 7.6 and 7.7 outline the necessary timing for the communication with the device.

Finally, check power supplies to see if there is significant ringing on the supply lines. If you have a lot of series inductances, this could cause a lot of voltage spiking because of the L(di/dt) that you see in digital currents.

It is also possible that you have bad connections on your board. You should visually inspect the connections to the device and see that there is good electrical contact from the device all the way to the microcontroller.

Read through these comments and check everything that I've mentioned. It's likely that the problem can be found through something that I've mentioned.


Joseph WU