ADC0MX setting
Signal Name
Enumeration Name
QFN24 Pin
Name
QSOP24 Pin
Name
QFN20 Pin
Name
10100 - 10111
ADC0.20 - ADC0.23
Reserved
Reserved
Reserved
11000
ADC0.24
ADC0P24
P2.1
P2.1
P2.1
11001 - 11011
ADC0.25 - ADC0.27
Reserved
Reserved
Reserved
11100
ADC0.28
USB_DP
USB D+ pin
11101
ADC0.29
USB_DM
USB D- pin
11110
ADC0.30
VREGIN_DIV_4
VREGIN / 4
11111
ADC0.31
NONE
No connection
12.3.4 Gain Setting
The ADC has gain settings of 1x and 0.5x. In 1x mode, the full scale reading of the ADC is determined directly by VREF. In 0.5x mode,
the full-scale reading of the ADC occurs when the input voltage is VREF x 2. The 0.5x gain setting can be useful to obtain a higher input
voltage range when using a small VREF voltage, or to measure input voltages that are between VREF and the supply voltage. Gain
settings for the ADC are controlled by the ADGN bit in register ADC0CF. Note that even with a gain setting of 0.5, voltages above the
supply rail cannot be measured directly by the ADC.
12.3.5 Initiating Conversions
A conversion can be initiated in many ways, depending on the programmed state of the ADCM bitfield. Conversions may be initiated by
one of the following:
1. Software-triggered—Writing a 1 to the ADBUSY bit initiates the conversion.
2. Hardware-triggered—An automatic internal event such as a timer overflow initiates the conversion.
3. External pin-triggered—A rising edge on the CNVSTR input signal initiates the conversion.
Writing a 1 to ADBUSY provides software control of ADC0 whereby conversions are performed "on-demand". All other trigger sources
occur autonomous to code execution. When the conversion is complete, the ADC posts the result to its output register and sets the
ADC interrupt flag (ADINT). ADINT may be used to trigger a system interrupts, if enabled, or polled by firmware.
During a conversion, the ADBUSY bit is set to logic 1 and reset to logic 0 when the conversion is complete. However, the ADBUSY bit
should not be used to poll for ADC conversion completion. The ADC0 interrupt flag (ADINT) should be used instead of the ADBUSY bit.
Converted data is available in the ADC0 data registers, ADC0H:ADC0L, when the conversion is complete.
Note:
The CNVSTR pin is a multi-function GPIO pin. When the CNVSTR input is used as the ADC conversion source, the associated
port pin should be skipped in the crossbar settings.
12.3.6 Input Tracking
Each ADC conversion must be preceded by a minimum tracking time to allow the voltage on the sampling capacitor to settle, and for
the converted result to be accurate.
EFM8UB3 Reference Manual
Analog-to-Digital Converter (ADC0)
silabs.com
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