Introduction

The Xilinx analog mixed signal module, referred to as the XADC, is a hard macro. It has JTAG and DRP interfaces for accessing the XADC’s status and control registers in the 7-series FPGAs.
Zynq-7000 AP SoC devices add a third interface, the PS-XADC interface for the PS software to control the XADC. The Zynq-7000 AP SoC devices combine a flexible analog-to-digital converter with programmable logic to address a broad range of analog data acquisition and monitoring requirements. The XADC is part of a larger analog mixed signal (AMS) topic that is a combination of analog and digital circuits.

HW/IP features

Analog-to-Digital Converters

• Dual 12-bit 1 MSPS analog-to-digital converters (ADCs)
• Up to 17 flexible and user-configurable analog inputs
• On-chip or external reference option
• On-chip temperature and power supply sensors
• JTAG access to ADC measurements

PS-XADC Interface

• Read and write XADC registers
• Serial data transfers to/from XADC
• Buffered read-write data operations
• 15-word by 32-bit command FIFO
• 15-word by 32-bit
• Read Data FIFO
• Programmable FIFO-level interrupts
• Programmable alarm interrupts
• Configured interface operations (using devcfg registers)
• DRP Parallel Interface
• Highest interface bandwidth
• 6-bit sample data

PL-JTAG Interface

• Access the XADC when the PL is not programmed but is powered-up
• Uses the JTAG TAP controller to access the XADC registers

Missing features, Known Issues, limitations

• System Monitor/ADC device can be accessed through the JTAG port and AXI interface. The driver implementation does not support the simultaneous access of the device by both these interfaces. The user has to care of this situation in the user application code.

Kernel configurations

To compile a kernel with a driver for the XADC enable the following kernel config option:

Device Tree Settings

Test Procedure

contains an user app called "xadc_app" for doing some sanity checks on sysmon driver.

Expected Output

Change Log

2016.3

• None

2016.4

• None

2017.1

• Fix external channel read issue

Commit Id: cefc6386c7cfc686681942be395b0cf3de6d88a3

• Fix error handling

Commit Id: acdbfc2832f380d42b80f78ff7e45645cc23ccd8

2017.2

• None

2017.3

• None

2017.4

• None

2018.1

• None

2018.2

• None

2018.3

• Check for return values in clk related functions
  • 493bdfcd664a
• Use devm_ functions while requesting irq
  • 87247cca78fe

2019.1

• None

2019.2

• None

2020.1

• None

Mainline status

XADC driver is in sync with the mainline kernel 5.4 except for the following
-> Reading the external auxiliary channels.
-> Support for ultrascale sysmon.
-> Limiting xadc pcap clock frequency value to be less than 200MHz.
-> Default values of extend_name in iio_chan_spec
->Reordering Error handling.

Related Links

• driver