Reverting changes made by PR #7520 and adjusting ADC

[HarukiToreda]

Summary

Reverts changes made by PR #7520 and adjusts the ADC calibration factor to 4.916.

The T114 originally used an ADC value of 4.90, based on the physical resistor divider on the board. PR #7520 raised this to 4.99 to artificially force the displayed battery voltage to read 4.19 V, which the firmware considers “100%” or fully charged. This approach ignores real-world battery behavior and introduces misleading readings.

To correct this, I decided to find a value that serves as a good medium across devices, prioritizing the display of the true voltage level over a cosmetic “fullness” percentage. I tested six different boards using an RK6006 programmable power supply set to a constant 4.14 V, ensuring the input source was not a variable.

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Why This Fix Is Needed

The firmware’s assumption that 4.19 V = 100% is flawed. In reality:

• Many batteries with built-in protection stop charging at 4.17 V.

• Some boards, like the T1114, cut off at 4.15 V.

By forcing the ADC to align with 4.19 V, the displayed voltage is inflated and no longer reflects the true battery state. This can cause issues for users who rely on accurate voltage for cutoff logic in solar or power-managed systems.

The previous calibration (4.90) reflected actual hardware, though subject to resistor tolerances. The adjustment to 4.99 only created a cosmetic “perfect” 100% while distorting actual values.

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Test Data (with ADC = 4.99 from PR #7520)

Node	Supplied Voltage	Displayed Voltage	Error
#1	4.14 V	4.20 V	+0.06 V
#2	4.14 V	4.19 V	+0.05 V
#3	4.14 V	4.19 V	+0.05 V
#4	4.14 V	4.16 V	+0.02 V
#5	4.14 V	4.25 V	+0.11 V
#6	4.14 V	4.18 V	+0.04 V

Error range: +0.02 V to +0.11 V (≈ 0.5%–2.7%)

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Test Data (with ADC = 4.916)

Node	Supplied Voltage	Displayed Voltage	Error
#1	4.14 V	4.14 V	0.00 V
#2	4.14 V	4.14 V	0.00 V
#3	4.14 V	4.14 V	0.00 V
#4	4.14 V	4.11 V	-0.03 V
#5	4.14 V	4.18 V	+0.04 V
#6	4.14 V	4.13 V	-0.01 V

Error range: −0.03 V to +0.04 V (≈ ±1%).

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Why 4.916

• Six boards tested, calibration factors ranged from 4.854–4.948.

• Average = 4.916, minimizing error across devices.

• Keeps readings within ±0.04 V of true.

• Grounded in repeatable hardware testing.

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Benefits

• Restores true hardware-based accuracy.

• Maintains error across devices below ±1%.

• Prevents misleading over-voltage reporting.

• Provides a single calibration factor validated across multiple devices.

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✅ In short: This PR reverts the artificial adjustment from #7520 and replaces it with a tested calibration factor (4.916), validated on six devices with a controlled 4.14 V supply.