ADC_battery Example

Source code path: example/rt_device/adc/adc_battery

Supported Platforms

The example can run on the following development board series.

  • sf32lb52-lcd series

  • sf32lb56-lcd series

  • sf32lb58-lcd series

Overview

  • Under the RT-Thread operating system, this example uses single-channel ADC sampling to read the VBAT battery voltage.

Usage

Build and Flash

  • This example uses ADC. Under RT-Thread, the ADC peripheral is virtualized as an rt_device for read and write operations. Make sure the rtconfig.h file in the current path contains the following macros:

#define BSP_USING_ADC 1
#define BSP_USING_ADC1 1
#define RT_USING_ADC 1

Only when these three macros are present will sifli_adc_init register the bat1 rt_device through rt_hw_adc_register, allowing rt_device_find and rt_device_control to succeed later.
Note
SiFli MCUs support timer interrupts to trigger simultaneous multi-channel sampling. Refer to the BSP_GPADC_SUPPORT_MULTI_CH_SAMPLING macro definition and the chip user manual.

  • If any of the three macros are missing, enable them with menuconfig using the following command:

sdk.py menuconfig –board=sf32lb52-lcd_n16r8 525 development board

sdk.py menuconfig –board=sf32lb52-lcd_52d 52d development board

As shown below, select GPADC1, save and exit menuconfig, then check whether the rtconfig.h macros were generated. alt text

  • Switch to the example project directory and run the scons command to build:

scons --board=sf32lb52-lcd_n16r8 -j8

  • Run build_sf32lb52-lcd_n16r8_hcpu\uart_download.bat and follow the prompts to select the serial port for download:

build_sf32lb52-lcd_52d_hcpu\uart_download.bat

Uart Download

please input the serial port num:5

Example Output:

The measured voltage is printed once per second in a loop.

  • Comparison of the voltage log before and after connecting the battery

alt text

  • Measurement test points for the 58_lcd and 56_lcd boards:

58 test points:

58

56 test points:

56

ADC Configuration Flow

  • Set the channel corresponding to the VBAT interface according to your board platform. This example uses channel 7 for the 52 series.

alt text

  • Set the ADC channel pin you want to measure to analog input mode (except channel 7 on the 52-series platform)

alt text

Note

  1. ADC input pins are fixed IOs, as shown below:
    The 52 series ADC CH1-7 mapping corresponds to software channels 0-6. The last channel, CH8 (Channel 7), is internally connected to VBAT sensing and is not mapped to an external IO.
    alt text

  2. For HAL_PIN_Set and HAL_PIN_Set_Analog, the last parameter selects HCPU or LCPU: 1 for HCPU, 0 for LCPU.

  • Use rt_device_find and rt_device_control to locate and configure the bat1 device interface in sequence. rt_adc_ops does not define rt_device_open, so skipping rt_device_open will not affect ADC functionality. It only affects whether bat1 appears as opened in list_device.

#define ADC_DEV_NAME        "bat1"      /* ADC1 device, already registered in rt_hw_adc_register, do not change arbitrarily */
#define ADC_DEV_CHANNEL     7           /* ADC channel selection, VBAT is fixed to CH8 (Channel 7) */
//#define REFER_VOLTAGE       330         /* ADC reference voltage, the 52 series can select 1.8 V or 3.3 V, but the interface is not exposed and is fixed at 3.3 V */
static rt_device_t s_adc_dev; /* Define an rt_device handle */
static rt_adc_cmd_read_arg_t read_arg;

void adc_example(void)
{
    rt_err_t r;

    /* Configure PA28 as analog input IO and do not enable internal pull-up or pull-down resistors */
    //HAL_PIN_Set_Analog(PAD_PA28, 1);

    /* Find the bat1 device. If BSP_USING_ADC1 is not enabled, the device will not be found and the system will hang */
    s_adc_dev = rt_device_find(ADC_DEV_NAME);

    /* Configure the sampling channel */
    read_arg.channel = ADC_DEV_CHANNEL;

    r = rt_adc_enable((rt_adc_device_t)s_adc_dev, read_arg.channel);
    
    /* This interface calls the sifli_adc_control function and reads only once. Users can process the data themselves. */   
    r = rt_device_control(s_adc_dev, RT_ADC_CMD_READ, &read_arg.channel);
    /* The logged value is in 0.1 mV units. 20846 means 2084.6 mV, or 2.0846 V. */
    LOG_I("adc channel:%d,value:%d",read_arg.channel,read_arg.value); /* (0.1mV), 20846 is 2084.6mV or 2.0846V */

    /* This demonstrates another way to perform ADC sampling. This interface calls sifli_get_adc_value and performs the default 22-sample average. */
    rt_uint32_t value = rt_adc_read((rt_adc_device_t)s_adc_dev, ADC_DEV_CHANNEL);
    /* The logged value is also in 0.1 mV units. 20700 means 2070.0 mV, or 2.0700 V. */
    LOG_I("rt_adc_read:%d,value:%d",read_arg.channel,value); /* (0.1mV), 20700 is 2070mV or 2.070V */

    /* Disable the ADC after sampling */
    rt_adc_disable((rt_adc_device_t)s_adc_dev, read_arg.channel);

}

Troubleshooting

  • The program crashes and prints the following log:

   Start adc demo!
   Assertion failed at function:rt_adc_enable, line number:144 ,(dev)
   Previous ISR enable 0

Reason:
BSP_USING_ADC1 is not defined, so rt_hw_adc_register does not register bat1. As a result, rt_device_find triggers an assertion failure when looking up the device.
Make sure the rtconfig.h file contains the following three macros:

#define BSP_USING_ADC 1
#define BSP_USING_ADC1 1
#define RT_USING_ADC 1

  • The sampled ADC voltage is incorrect

  1. Use the list_device command to check whether the bat1 device exists. The ADC driver is not affected even if bat1 is not opened with rt_device_open.

    msh />
 TX:list_device
    list_device
    device           type         ref count
    -------- -------------------- ----------
    audcodec Sound Device         0       
    audprc   Sound Device         0       
    rtc      RTC                  0       
    pwm3     Miscellaneous Device 0       
    pwm2     Miscellaneous Device 0       
    touch    Graphic Device       0       
    lcdlight Character Device     0       
    lcd      Graphic Device       0       
    bat1     Miscellaneous Device 0       
    i2c4     I2C Bus              0       
    i2c1     I2C Bus              0       
    spi1     SPI Bus              0       
    lptim1   Timer Device         0       
    btim1    Timer Device         0       
    gptim1   Timer Device         0       
    uart2    Character Device     0       
    uart1    Character Device     2       
    pin      Miscellaneous Device 0       
    msh />

  1. Check whether the ADC hardware is connected correctly. ADC sampling channels map to fixed IO pins and cannot be assigned arbitrarily. Refer to the chip manual for the CH0-7 pin mapping.

  2. The ADC input voltage range is 0 V to the reference voltage (3.3 V by default on the 52 series). Do not exceed the input range.

  • ADC accuracy is insufficient

  1. Check whether ADC calibration parameters are obtained and applied.

  2. Check whether the voltage divider resistor accuracy meets the requirement.

  3. Check whether the ADC reference voltage is stable and has excessive ripple. Refer to the ADC reference documentation in the chip manual for details.

Reference Documents

  • EH-SF32LB52X_Pin_config_V1.3.0_20231110.xlsx

  • DS0052-SF32LB52x Chip Technical Specification V0p3.pdf

  • RT-Thread Official Website
    https://www.rt-thread.org/document/site/#/rt-thread-version/rt-thread-standard/programming-manual/device/adc/adc

Revision History

Version

Date

Release Notes

0.0.1

11/2024

Initial version

0.0.2

05/2026

Added notes for 56 and 58