Hi there,
I'm working with a stand-alone ADS1248 EVM and am trying to hook it up to my EKS-LM4F232. I'm having issues with the internal reference, though. I use this piece of code to turn on the internal reference and select it for use in conversions:
//write to MUX1 to set up internal reference
ROM_SSIDataPut(SSI3_BASE, 0x42);
ROM_SSIDataPut(SSI3_BASE, 0x00); //0x00 is # of bytes to write minus 1
ROM_SSIDataPut(SSI3_BASE, 0x30); //0x30 sets up internal reference for use
When I measure the internal reference on the board, it is always 0V and not the expected 2.048V. So, whatever analog input I try to measure spits back the maximal return value (this is even the case when I use the system monitor to measure the internal temperature diode.) (I'm just in a test phase...the ADS1248 is running in SDATAC mode; I keep start and reset tied high and just request conversion results periodically.) I've confirmed, by reading the MUX1 register, that the ADS1248 has been configured appropriately. I'm not sure what could be going wrong.
Obviously, the culprit could be my connections. Here's how I have everything connected:
Jumper J7 Serial Interface Pins:
J7.1: is connected to CS (FSS) on my Stellaris board
J7.2: is tied high.
J7.3: is connected to the SPICLK on my Stellaris board.
J7.4: is grounded.
J7.5: unusued
J7.6: is tied high
J7.7: unused
J7.8: unusued
J7.9: unused (I'm not monitoring DRDY to get conversions)
J7.10: is grounded.
J7.11: attached to SPITx on my Stellaris board
J7.12: unused
J7.13: attached to SPIRx on my Stellaris board
J14-17: unused
J18: grounded
J19-20: unused
Jumper J11: Power-Supply Input:
J11.1 - J11.2: unused
J11.3: connected to 5V from a power supply
J11.4: grounded
J11.5: connected to ground on my Stellaris board
J11.6: connected to the ground from my 5V power supply
J11.7-8: unused
J11.9: connected to 3.3V output off of my Stellaris board
J11.10: unused
Jumper J1 is in position 1-2.
I really appreciate any feedback. Thank you!
-David