Using mBed 1768 microcontroller and breadboard, and the mBed compiler for code.
ID: 3582722 • Letter: U
Question
Using mBed 1768 microcontroller and breadboard, and the mBed compiler for code. Give an example of how a single ADC can be used to sample four different analog signals. You will need to present one possible solution including the hardware connection (pin connection), code stub (code block) that samples each of the analog signals in sequence and stores them in four separate variables s1, s2, s3, and s4 respectively.
VIN 14.0v miso SP sck 12C Serial 11 mos 12 miso SPI Serial Analogin 18 UIN RO TO 28 101 ESV Regulated Ethernet USB 12C Serial out RD RD+ TD. TD+ 29 28 25 22Explanation / Answer
Answer:
All the ADC blocks of the F28xx/F28xxx devices have internal bandgap reference voltage source. The only reason for going for external voltage source is the temperature stability. The temperature coefficient of the internal voltage source is 50 PPM/C. If your end product requires good ADC accuracy over a wider temperature variation, you need to select an external reference voltage source that requires lower value temperature coefficient. While doing so, it is important that you use a low output impedance op-amp buffer so that signal is stable during the conversions. Do not connect this node to any other input or load circuit on the design. It is important that noise on the reference input pins be less than 100 V. • Connecting an external voltage reference for the F280x, F280xx and F2833x devices: The ADC blocks of these parts require a single reference voltage input to be connected between the ADCREFIN and ADCLO pins. Based on customer application requirements, the ADC logic can be supplied by an external voltage reference. The F280x ADC accepts 2.048 V, 1.5 V, or 1.024 V on the ADCREFIN pin. You also need to set a two-bit field of the ADC Reference Select Register according to the voltage level of the external source to enable the external reference and determine the reference source selected.
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