[BUG] MKS TinyBee wrong temp reported on 2.0.9.3 & Bugfix

[countcobolt]

Did you test the latest bugfix-2.0.x code?

Yes, and the problem still exists.

Bug Description

The firmware is reporting wrong temperatures of the thermistors. On the original MKS version (https://github.com/makerbase-mks/MKS-TinyBee/tree/main/firmware/mks%20tinybee%20marlin) , I get a proper read out of the temperature (in °C, 21 bed, 27 hotend).

When building either Bugfix or 2.0.9.3 I get wrong reading. Bugfix is reading 0 and 1°C for both bed and hotend, while the 2.0.9.3 is reading a lot higher temperature around 70°C.

Now, when I revert back to the MKS version, the temperatures are back correct, indicating that this is not a thermistor or machine error.

I have updated the pins_MKS_TINYBEE.h but only tried to add the ADC reading and the filament out pin.

No other changes to the 2.0.9.3 version or bugfix.

Bug Timeline

new

Expected behavior

The right temperature to show on all firmware versions

Actual behavior

Wrong temp on bugfix and 2.0.9.3

Steps to Reproduce

Install MKS version of firmware (2.0.9.2 branch)
Check temperature
Build either bugfix or 2.0.9.3
Check temperature
Difference is hug
MKS_Original.zip
20903_config.zip
e

Version of Marlin Firmware

2.0.9.2 MKS version

Printer model

CR10 heavy modified

Electronics

MKS Tinybee board

Add-ons

No response

Bed Leveling

ABL Bilinear mesh

Your Slicer

Cura

Host Software

OctoPrint

Additional information & file uploads

I have upload the original config that is working (MKS_Original, this does contain the changes for my machine) and the 2.0.9.3 configuration that is showing the wrong version. Bugfix I did not keep but can provide if needed.

[countcobolt]

Solved by using solution in here makerbase-mks/MKS-TinyBee#7

[ellensp]

That is already in bugfix...

with this in Marlin/src/pins/esp32/pins_MKS_TINYBEE.h

//
// ADC Reference Voltage
//
#define ADC_REFERENCE_VOLTAGE                2.5  // 2.5V reference VDDA

and ths is the HAL

#ifndef ADC_REFERENCE_VOLTAGE
  #define ADC_REFERENCE_VOLTAGE 3.3
#endif

ie set to 2.5 for MKS_TINYBEE

then used here

void MarlinHAL::adc_start(const pin_t pin) {
  const adc1_channel_t chan = get_channel(pin);
  uint32_t mv;
  esp_adc_cal_get_voltage((adc_channel_t)chan, &characteristics[attenuations[chan]], &mv);

  adc_result = mv * isr_float_t(1023) / isr_float_t(ADC_REFERENCE_VOLTAGE) / isr_float_t(1000);

[3DSmitty]

Why are we setting the ADC_REFERENCE_VOLTAGE to 2.5? This did not work for me I was getting incorrect temp readings. I had to change it to 2.6 to get the correct temp readings. I have thermistor type 11 for both extruder and bed.

[bebu]

When you take a look at mks provided firmware they do this:

  // HAL_adc_result = mv * 1023.0 / 3300.0;
  HAL_adc_result = mv * 1023.0 / 2570.0;

I had similar problems with 2.5 so i set it to 2.57. Which is similar to what you have seen.

[3DSmitty]

I ended up playing around with the value to get:

#define ADC_REFERENCE_VOLTAGE 2.565

Setting it to 2.565 gives me +-1C degree accuracy.

[thisiskeithb]

Setting it to 2.565 gives me +-1C degree accuracy.

I've submitted a PR to update this: #24432

[3DSmitty]

@thisiskeithb Thanks!

[github-actions]

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