Silicon Laboratories EMBER EM358 series, Reference Manual, Page: 221 / 257

EM358x
Rev. 0.4 221
11 ADC (Analog to Digital Converter)
The EM358x ADC is a first-order sigma-delta converter with the following features:
 Resolution of up to 14 bits

Sample times as fast as 5.33 µs (188 kHz)
 Differential and single-ended conversions from six external and four internal sources
 One voltage range (differential): -VREF to +VREF

Choice of internal or external VREF
 internal VREF may be output to PB0 or external VREF may be derived from PB0
 Digital offset and gain correction

Dedicated DMA channel with one-shot and continuous operating modes
Figure 11-1 shows the basic ADC structure.
Figure 11-1. ADC Block Diagram
While the ADC Module supports both single-ended and differential inputs, the ADC input stage always operates in
differential mode. Single-ended conversions are performed by connecting one of the differential inputs to VREF/2
while fully differential operation uses two external inputs.
Note:
The regulator input voltage, VDD_PADS, cannot be measured using the ADC, but it can be measured
through Ember software.
11.1 Setup and Configuration
To use the ADC follow this procedure, described in more detail in the next sections:

Configure any GPIO pins to be used by the ADC in analog mode.

Configure the voltage reference (internal or external).

Set the offset and gain values.

If using DMA, reset the ADC DMA, define the DMA buffer, and start the DMA in the proper transfer mode.

If interrupts will be used, configure the top-level and second-level ADC interrupt bits.

Write the ADC configuration register to define the inputs, sample time, and start the conversions.