I am trying to connect one of the ADS1118EVM boards (without the usb reader) from a beaglebone black using embedded linux kernel 3.2
I am unable to get proper values even though I believe I have the waveforms for SCLK DI constructed properly. I am reading DI shortly after I take SCLK high, (with a short delay). One question I have is there a minimum SCLK frequency that the ADS1118 can use?
I am using a Chipsee Cape with a 7" LCD with capacitive touch which all works properly. I cannot use the built in OMAP SPI ports because they are all in use and I need something that works sooner than it will take me to rip their kernel source apart and come up with a proper driver. That is why I am trying to bitbang using the few GPIO pins I have left.
I am attaching a couple of scope photos so you can see the waveforms. CS is tied low. I have tried using it as well and it does not help.
My program sends 0x3d0b to initialize the config register. The later to do a reading it sends 0xbd0b to start a conversion and the about 30ms later it sends a 0xffff nop command to read the value that should be T2-3.
This should be +- 0.256 volts FS and 8SPS
You can see from the scope pictures that the ads1118 is not returning the config values I send much less the data values.
This code sequence is from looking at the sample labview program running in monitor mode for T2-3. This seems to be the code sequence that progam uses.
Any help will be much appreciated. I have bitbanged i2c interfaces before and a couple of SPI and have never had this much trouble!
Thanks,
Jim Jones
Sending 0xBD0B
NOP for reading values after conversion is done.
