IDAC USER GUIDE

---

REVISION HISTORY

Revision No.	Description	Date
1.0	Initial release	05/08/2025

1. Overview

DAC (Digital to Analog Converter) is an electronic device that converts digital signals into analog signals. We usually use DAC to refer to voltage output type DAC (i.e. the output analog signal is voltage), and IDAC to refer to current output type DAC (i.e. the output analog signal is current).

2. Keyword

• DAC

  (Digital-to-Analog Converter) A digital to analog converter is an electronic device that converts digital signals into analog signals.

• IDAC

  (Current Digital-to-Analog Converter) Current Digital to Analog Converter is a type of digital to analog converter that uses current as the output analog signal.

3. FUNCTION DESCRIPTION

There are two voltage regulation methods: VID and IDAC. VID voltage regulation is achieved by controlling 1-2 GPIO to adjust the voltage, with only 2-4 voltage levels available for adjustment. The accuracy between different levels is around 50mV. IDAC voltage regulation can more finely adjust the voltage (with a precision of 10mV or 20mV), and only requires a dedicated GPIO to control up to 30 voltage levels.

4. HARDWARE CONNECTION INTRODUCTION

The IDAC hardware module is integrated within the SoC. It is necessary to switch the corresponding jump cap on the development board to IDAC mode to enable IDAC voltage regulation function.

5. Uboot USAGE INTRODUCTION

Using the set command in uboot to modify the power scheme. The command usage description is as follows：

Usage:
set overdrive 0 - change power scheme to 'Low Drive - LD'
set overdrive 1 - change power scheme to 'None Overdrive - NOD'
set overdrive 2 - change power scheme to 'Over Drive - OD'
set overdrive 3 - change power scheme to 'Turn Off'

6. Kernel USAGE INTRODUCTION

The objects of IDAC voltage regulation include Core Power（VDD_CORE），CPU Power（VDD_CPU），IPU Power（VDD_IPU），DSP Power（VDD_DSP） Wait. The voltage regulation objects supported by different platforms may vary. Taking the example of adjusting CPU Power with IDAC on the IFORD platform, the following will illustrate.

6.1. Configure Kennel Config

1. Enable corresponding driver module:

   The following configurations need to be selected when compiling the kernel:

   Device Drivers  --->
       [*] Sstar SoC platform drivers  --->
           [*] Sstar Voltage IDAC Control
   

6.2. Configure DTS

The relevant settings for IDAC to control CPU Power are in the cpu_power node in dts. The parameters in the node are as follows:

1.    cpu_power {
2.        compatible = "sstar,voltage-idac-ctrl";
3.        vid_gpio = <PAD_PM_GPIO5>;
4.        base_voltage = <900>;
5.        status = "okay";
6.    }；

The meanings of the attributes in the cpu_power node are as follows:：

Attribute	Desciiption	Set Value	Notes
compatible	Match driver for driver registration	"sstar,voltage-idac-ctrl"	Prohibit modification
vid_gpio	GPIO used for configuration	Hardware decision	Prohibit modification
base_voltage	Reference voltage (in mV)	Hardware decision	Prohibit modification
status	Select whether to enable the node	"okay" or "disabled"	Modify as needed

6.3. Configure Padmux

NA

6.4. Module Usage Introduction

6.4.1. SYSFS Usage method

Using sysfs to query/modify CPU power in the kernel, the instructions are as follows:

• CPU Power

  Dump current CPU power

  cat /sys/devices/system/voltage/cpu_power/voltage_current
  
  1070
      VOLTAGE_DEMANDER_INIT           -
      VOLTAGE_DEMANDER_CPUFREQ        1070
      VOLTAGE_DEMANDER_TEMPERATURE    -
      VOLTAGE_DEMANDER_USER           -
  

  Query available cpu power

  cat /sys/devices/system/voltage/cpu_power/voltage_available
  Vmin(mV)        Vmax(mV)
  700         1300
  

  Set cpu power to 900mV

  echo 900 > /sys/devices/system/voltage/cpu_power/voltage_current
  

---

6.4.2. ioctl Usage method

N/A

6.5. Sample Code

N/A

7. API Reference

This functional module provides the following interfaces:

Parameter Name	Description
set_core_voltage	set voltage
get_core_voltage	get voltage

7.1. set_core_voltage

• Function

  Set voltage

• Grammar

  int set_core_voltage(const char *name, VOLTAGE_DEMANDER_E demander, u32 mV)
  

• Parameter

  Parameter Name	Description
  name	The name of the object that needs to be setting，such as ore_power，cpu_power，ipu_power
  demander	Requester
  mV	Voltage value (unit: mv)

• Return value

  Return value	Description
  0	Successful
  other	Fail

7.2. get_core_voltage

• Function

  Get voltage

• Grammar

   int get_core_voltage(const char *name, u32 *mV)
  

• Parameter

  Parameter Name	Description
  name	The name of the object to be queried, such as core_power，cpu_power，ipu_power
  mV	The voltage value retrieved is retained in this variable

• Return value

  Return value	Description
  0	Successful
  other	Fail

8. FAQ

NA