I am unable to read from or write to the AD7928 analog to digital converter (ADC) on the DE1-SoC (Rev. F) development board.
I have the datasheets for the board and the ADC. I am using a mix of custom IP and pre-made hardware components. I have implemented the LEDs, push buttons, and 7-segment displays in Qsys along with the ADC. Base addresses and ranges are set for the memory space of each component. I am controlling the hardware with a C program running in Linux on the dev board. Using a virtual address and offset, I can control all the aforementioned components except the ADC.
The datasheet for the ADC shows 8 registers for reading and 2 for writing. The ADC is set up in Qsys to use one channel (channel 0) out the 8 channels available, running at 12.5MHz. The memory range in Qsys shows correctly that there are 32bytes of addressing assigned to the ADC (8 registers at 4 bytes each). Two of the registers share a read and write command.
Here are the pointers I use for writing the Auto Enable command and reading the 12-bit temperature from channel 0 of the ADC:
// Set ADC to automatically update (write to register offset 4)
*(uint32_t *)(h2p_lw_adc_addr + 4) = 1;
// Read channel 0 from the ADC (read from register offset 0)
temp_in = *(uint32_t *)h2p_lw_adc_addr;
I use the same pointer set-up with the other components, which all work.
I looked at the soft-core processor set-up for the ADC and it has a .h file that contains a command to turn the ADC on, but it seems the hard-core processor systems does not have that command.
Is there some other set-up required for the ADC to be able to use it with the HPS (hard-core processor sys)? The ADC datasheet only shows the 8 registers for control and I have tried both the Auto Enable and Begin Conversion modes. The command registers are shown below.
