Other Parts Discussed in Thread: ADS7952
Hi,
I have an ADS7952 chip with the following hardware configuration:
- +VA: 5V
- +VBD: 3.3V
- REFP: 2.5V
- Channels 4-11 in use, channels 0-3 unused
- GPIO unused
When I start up, I send two configuration frames, 0x8000 and 0x0FF0, to set up Auto-1 mode with the set of channels I am using. Then I poll with the frame 0x2040 to view the analog channels. The data coming back looks great except that it appears to be stuck in Range 1 (0 - Vref) instead of Range 2 (0 - 2*Vref) ... for an input of about 1.13 volts I get 1851 counts (0x73B) instead of the expected 912. Similarly for an input of 2.75V I get 0xFFF (full scale) instead of just over half.
I checked the MXO & AinP pins and confirmed that the input voltages are correct. The displayed voltages look excellent and the output is responsive to changing inputs, it just appears to be set at Range 1.
One thing I have noticed is that when I power up, I send the configuration frames and start polling, but don't receive anything from the MXO pin for about 80 polls. To be sure, when I start receiving data, I stop polling for a bit and re-send the configuration registers (it doesn't seem to make any difference).
Here's me sending the configuration registers the second time:
... and then here is polling and receiving data about two channels, which both have input voltages around 1.15 ± 0.05:
Any thoughts on what might be going on here? Thanks!
