Hello Benjamin,
Thanks for your message.
Have you issued the same write commands as before - i.e. configure the test tone and then issued the command to the ECGCTL register to start converting data? (this did work for you previously).
The fact that you are seeing the READY bit = 1 suggests to me that the ADAS1000 conversion is not ready yet, the internal filters can take some time initially to settle (when start converting), so if you keep reading frames, after some time the header contents should become READY = 0 and you should see valid data again...
Hope this helps.
best regards,
Catherine.