STM8T141 Programming Tips

[eugenio]

Posted on November 23, 2011 at 12:10

Hello,

we would like to use the STM8T141 part for proximity sensors. The question is the following:

We need to disable the environmental compensation filter (ECF) as in our opinion this will cause troubles as the sensor application imply a a gradual change in the capacitance under observation up to the detection point and this could move the reference level along with the slow capacitance variation producing a missing detection.

For our application the reference level must be fixed and not re-setup at chip startup.

Can anyone help us on this?

BR

eugenio

[Thierry GUILHOT]

Posted on November 23, 2011 at 14:50

Hi,

Using STM8T141 and STM8T142 devices, it is not possible to disable the ECS. However, the new STM8T143 device offers a control mode which allows to control the ECS operation. Using this feature, it is thus possible to disable the ECS. However, doing this may also generate some issues and it must be thus carefully tested. Indeed, the ECS being disabled, the system is no more in position to track slow environment changes such as temperature, voltage drift, capacitance drift, … This can then generate some false detections.

However, it is important to note that a calibration process will always take place at the device startup and upon touch detection (DYCAL feature) to ensure correct system operation and optimum proximity/touch detection.

Best Regards,

Thierry,

Hello,

we would like to use the STM8T141 part for proximity sensors. The question is the following:

We need to disable the environmental compensation filter (ECF) as in our opinion this will cause troubles as the sensor application imply a a gradual change in the capacitance under observation up to the detection point and this could move the reference level along with the slow capacitance variation producing a missing detection.

For our application the reference level must be fixed and not re-setup at chip startup.

Can anyone help us on this?

BR

eugenio

[eugenio]

Posted on November 24, 2011 at 10:51

hi Thierry,

Many thanks for your support.

Maybe I have misunderstood the meaning of ECS and calibration at start up. I will give you the picture of our industrial application in order to avoid confusion.

We need to use the device in proximity mode detecting the presence/absence of small plastic grains in a tank. The level of grains will decrease slowly towards the end and the

Sensor should advise when this happens. The level of grains decreases very slowly so the ECS would follow this capacitance change and adapt the internal track accordingly and

This missing afterwards the absence of grains in front of the sensor. Moreover at power start up the sensor would adapt it's internal level to current situation but in proximity situation

you have should have digital response present not present. Correct?

BR

Eugenio