Time for a first raw ADC test for Road test: Renesas Solution Starter Kit for RX23E-A. This is a first step to check (and learn) the analogue capacities of the RX23E-A.
On the starter kit, I'm using the default firmware and default setup. AIN3 and AIN2 take the analogue circuitry. As sample signal, I use a AD584KH voltage reference I recently purchased.
The default config uses the internal 2.5 V reference, and bypasses the analogue front end. The signal directly enters into the ADC. No gain, no buffers.
Renesas uses DSAD as acronym for the ADCs in its documentation. It stands for Delta-Sigma A/D Converter.
I powered the kit before turning on the voltage reference. This to take care that the inputs never exceed the limits documented in the "absolute maximums" section of the controller's user guide.
Then I let the PC Tool take a few 100 samples. Here are the results:
max: 8383103
min: 8381812
The PC Tool calculated the mean of all samples: 8382488
As effective number of bits (ENOB), it reports: 16 (the ADCs are sigma-delta 24 bit converters)
How does this translate to voltage? This is the formula to derive the voltage form the digitised value:
VID = (2.5 * 2) / 1 * 8382488 / 2^24 (V)
= 5 * 8382488 / 16777216
= 2.498176 V
according to the label on my voltage reference, it outputs 2.49974 V (measured with an HP3458A)
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challenge: this is a 24 bit ADC. Snippet from the Analog Front End specs
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Some captures of the PC Tool, zooming in on the "ac component"
full screen is 100 ms
full screen is 10000 ms:
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