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G120 Analog Input Range

Posted 4yr ago
by mhardy | Junior | 590 exp
Posted 4yr ago
by mhardy | Junior | 590 exp
The user manual (March 9, 2015) say's the G120 has 10 bit analogs (0-1023).

AnalogInput.ReadRaw() is returning values from 0-4095, indicating the G120 has 12 bit analogs.

I assume the user manual is incorrect, right?

btw: My custom board has circuitry connecting the analog inputs to sensors that are 4-20mA, when I max the sensor out (20mA) I am seeing the digital analog count value = 4095
Reply #1 — Posted 4yr ago
by Brett | Superhuman | 125,590 exp
Reply #1 — Posted 4yr ago
by Brett | Superhuman | 125,590 exp
Voltage != current.

4095 when reading an analog line simply means the voltage is 3.3v.
Reply #2 — Posted 4yr ago
by mhardy | Junior | 590 exp
Reply #2 — Posted 4yr ago
by mhardy | Junior | 590 exp
Yes Brett... I fully understand how analogs work!
My circuitry converts current to volts, where 20mA = 3.3V.
At 3.3V on the analog pin, I am seeing a count = 4095.

The manual says the analogs are 10bit (0-1023)....but I am seeing 4095 (12bit).

I am asking for verification that the manual is incorrect?
Reply #3 — Posted 4yr ago
by Brett | Superhuman | 125,590 exp
Reply #3 — Posted 4yr ago
by Brett | Superhuman | 125,590 exp
so your "sensor" outputs 3.3v when the real sensor outputs 20mA. Great. Better to explain it that way Smiley

So now the ONLY ask is for someone to confirm the G120 manual under-states the resolution for the ADC. Should be 12-bit not the 10-bit as documented.
Reply #4 — Posted 4yr ago
by mhardy | Junior | 590 exp
Reply #4 — Posted 4yr ago
by mhardy | Junior | 590 exp
Yes - just looking for confirmation from GHI.

The NXP LPC1788 User manual states:

12-bit Analog-to-Digital Converter (ADC) with input multiplexing among eight pins,
conversion rates up to 400 kHz, and multiple result registers.
The 12-bit ADC can be used with the GPDMA controller.
-
10-bit Digital-to-Analog Converter (DAC) with dedicated conversion timer and DMA
support
Reply #5 — Posted 4yr ago
by John_ghielectroncs | Employee
Reply #5 — Posted 4yr ago
by John_ghielectroncs | Employee
@mhardy - You are correct. Analog input has 12 bit resolution. The manual has been updated.
Reply #6 — Posted 4yr ago
by mhardy | Junior | 590 exp
Reply #6 — Posted 4yr ago
by mhardy | Junior | 590 exp
Thanks for the verification and quick update to the user manual...

FYI,
The manual still has a misprint stating that analogs are 10-Bit, however.

Section:
1.3.G120 Module Key Features
.
.
.
.
8 10-Bit Analog Input
Reply #7 — Posted 4yr ago
by John_ghielectroncs | Employee
Reply #7 — Posted 4yr ago
by John_ghielectroncs | Employee
@mhardy - Thanks again, it's been fixed.

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