2.2. ADC16

2.2.1. Overview

• This example shows ADC16 conversions and results in four working modes.

Notes:

• When ADC is configured to non-bus-read (oneshot) mode, it can’t be accessed otherwise bus will be stuck.

• When ADC is configured to bus-read (oneshot) mode, CPU has to complete initialization before accessing to the ADC register list.

2.2.2. Board Setting

• Input voltage at the specified pin. （Please refer to Pin Description）

• If necessary, connect a jumper for VREF pin according to the HW design. （Please refer to Pin Description）

Note: The input voltage range at ADC input pins: 0~VREFH

2.2.3. Running the example

• Running log is shown in the serial terminal as follows

This is an ADC16 demo:
1. Oneshot    mode
2. Period     mode
3. Sequence   mode
4. Preemption mode
Please enter one of ADC conversion modes above (e.g. 1 or 2 ...):

• Select one of ADC working modes to start ADC conversion, and then watch conversion results

  • Oneshot mode

  Please enter one of ADC conversion modes above (e.g. 1 or 2 ...): 1
  Oneshot Mode - ADC3 [channel 2] - Result: 0xffe8
  Oneshot Mode - ADC3 [channel 2] - Result: 0xfff4
  Oneshot Mode - ADC3 [channel 2] - Result: 0xffff
  

  • Period mode

  Please enter one of ADC conversion modes above (e.g. 1 or 2 ...): 2
  Period Mode - ADC3 [channel 2] - Result: 0xfff3
  Period Mode - ADC3 [channel 2] - Result: 0xfff5
  Period Mode - ADC3 [channel 2] - Result: 0xfff7
  

  • Sequence mode

  Please enter one of ADC conversion modes above (e.g. 1 or 2 ...): 3
  Sequence Mode - ADC3 - Cycle Bit: 01 - Sequence Number:00 - ADC Channel: 02 - Result: 0xffff
  Sequence Mode - ADC3 - Cycle Bit: 00 - Sequence Number:00 - ADC Channel: 02 - Result: 0xffd9
  Sequence Mode - ADC3 - Cycle Bit: 01 - Sequence Number:00 - ADC Channel: 02 - Result: 0xffff
  

  • Preemption mode

  Please enter one of ADC conversion modes above (e.g. 1 or 2 ...): 4
  Preemption Mode - ADC3 - Trigger Channel: 00 - Cycle Bit: 01 - Sequence Number: 00 - ADC Channel: 02 - Result: 0xffff
  Preemption Mode - ADC3 - Trigger Channel: 00 - Cycle Bit: 01 - Sequence Number: 00 - ADC Channel: 02 - Result: 0xffff
  Preemption Mode - ADC3 - Trigger Channel: 00 - Cycle Bit: 01 - Sequence Number: 00 - ADC Channel: 02 - Result: 0xffff
  

2.2.4. Note

• How to use WDOG feature

  • Channel initialization

    • Set ch_cfg. wdog_int_en to true

    • Set ch_cfg.thshdl/ch_cfg.thshdh

      The ch_cfg.thshdl/ch_cfg.thshdh can be configured from 0 to 65535. If any ADC conversion result is out of the thresholds (thshdl, thsdhh), a WDOG interrupt will occur.

  • Call adc16_init_channel () API.

  • ISR

    • Set one or more WDOG event flags depending on ADC channels

    • Disable one or more corresponding WDOG interrupts

  • Main loop

    • Handle with WDOG events

    • Enable one or more corresponding WDOG interrupts

• Trigger source

  • In this sample, for sequence mode and preemption mode, PWM is selected as the trigger source. Other peripherals can also be selected as the trigger source.

  • The frequency of the trigger signal(20KHz by default) can be configured in sample-level CMakeLists.txt(e.g. sdk_compile_definitions(-DAPP_ADC16_TRIG_SRC_FREQUENCY=20000))

• Exception exit

  Press the “space” key to abort the test, and then a test mode can be reselected.