SDADC_HAL Example

Source code path: example/hal/adc/sdadc

Overview

  • Uses the HAL API to operate the SDADC directly, implementing single-channel voltage sampling.

Supported Platforms

The example can run on the following development board.

  • sf32lb58 HDK

Note: The SDADC IP is only available on SF32LB55X and SF32LB58X chips. This example was debugged on the 58 series.

Hardware Connection

Mapping between SDADC channels and pins:

Chip

CH1

CH2

CH3

CH4

SF32LB55X

PB_23

PB_24

PB_25

PB_26

SF32LB58X

PB_40

PB_41

PB_42

PB_43

CH0 is only used for BGA packages and is not available on regular GPIO.

Connect the target SDADC pin to an external voltage source (0 ~ 3.3V). GND must share a common ground with the board.

Usage

Build and Flash

  • This example uses the HAL layer API. Make sure the SDADC module is enabled in rtconfig.h:

#define BSP_USING_SDADC 1

  • Switch to the example project directory and run scons to build (using ec-lb587 as an example):

scons --board=ec-lb587_hcpu -j8

  • Run build_xxx_hcpu\uart_download.bat and follow the prompts to select the port for download.

Example Output:

Using CH3 (58x: PB_42) as an example, the register value and converted voltage are printed in a loop once per second:

======== SDADC HAL Example ========
Chip: SF32LB58X
Test channel: 3 (CH3)
Calibrate: sdadc_cal <reg1> <mV1> <reg2> <mV2>
SDADC factory calib not found, using defaults
  offset=961912, ratio=7068 (×1000000)
SDADC channel 3 pinmux configured (gain=1/4)
SDADC Init done
Waiting 2s for VREF to stabilize...
msh >
SDADC channel 3 configured, ready
Reading SDADC every 1 second...
SDADC ch3: reg=1055680 (min=1041502 max=1062947), voltage=662 mV

  • In the floating state, the reading is about 600~700 mV (the SDADC has a high-impedance input; the floating value is affected by the environment, which is normal).

  • After connecting a known voltage source, the reading should be close to the actual voltage.

  • The register value reg is the 24-bit raw output, and voltage is the converted value in mV.

Calibration

If the chip has not been SDADC-calibrated, you can send the following command to perform a two-point calibration:

sdadc_cal <reg1> <mV1> <reg2> <mV2>

For example, connect 1.2V and 2.6V voltage sources, record the two reg values, and send over the serial port:

sdadc_cal 1083587 1200 1268771 2600

Calibration values are lost after a reboot.

Troubleshooting

  • The log shows Invalid SDADC channel

    • SDADC_TEST_CHANNEL selects an invalid channel

  • The log shows SDADC poll timeout!

    • The SDADC conversion did not complete; check the pin configuration and whether the reference voltage is normal.

  • Readings are abnormal or deviate significantly from the actual voltage

    • Missing calibration values cause abnormal data; run sdadc_cal to calibrate manually.

Revision History

Version

Date

Release Notes

0.0.1

07/2026

Initial version