CCS/MSP430G2553: Dispersion between MSP430G2553 units in capacitance measurement

ERNESTO GALIANO

Part Number: MSP430G2553
Other Parts Discussed in Thread: MSP430FR2512

Tool/software: Code Composer Studio

HI.
I am using an MSP430G2553, for a capacitive sensor that measures up to 200pf, with the Pin Oscillator method, shown in figure 8.1 of document SLAU144J. I use the Pinosc_01 example of MSP430Ware
Try a microcontroller with the pcb, and in the tests everything worked fine.
When I test several microcontrollers, an operating dispersion appears, more in the average measurement area than in the extremes, it reaches 3% and I need to reduce it to 1%.
I will try adding a crystal, and varying the timings so that the measurement value is as high as possible.
Any other idea? Maybe some other newer micro with Captivate technology is better?

over 6 years ago

0 Kostas Aslanidis over 6 years ago

TI__Intellectual 2885 points

Hi Ernesto,
we have a capacitive touch solution called CapTIvate. This is a high performance, robust and noise immune system based on a MSP430.

www.ti.com/.../overview.html

You may have a look in this product family and it's features for more details.
Please check also our training section, where you can find a lot of training materials and TI design
training.ti.com/captivate-training-series

As I understand, you need just one capacitive sensor. We do have also some devices in this family with only 4 capacitive touch IO which may be of interest for you application e.g. MSP430FR2512, but you may also check the memory size and peripherals.

In general to your application, I am not sure I fully understand the implementation and the requirements. Please check if CapTIvate can be a solution for your application.

Regards
Kostas

0 Otto.C over 6 years ago

Expert 1045 points

hi,

If your design is still flexible, here is another technique which you may choose to consider:
- using the comparator on the G2553.
- www.ti.com/.../slaa071.pdf
check section 2.7
It describes measuring the charge time of the unknown capacitor (using a TA module trigged by Comparator) as its voltage ramps up through a known resistor. A Port pin going low to high starts the process.

This is a trusted and reliable method.

0 Kostas Aslanidis over 6 years ago in reply to Otto.C

TI__Intellectual 2885 points

Hi Ernesto,
could you please let us know if the information above was helpful and you could find a way to solve the issue.

Thanks
Kostas

0 ERNESTO GALIANO over 6 years ago in reply to Kostas Aslanidis

Prodigy 140 points

Hi Costas,
This answer helped me in the sense of using methods that depend on components in which I can modify their accuracy if necessary.
Many thanks

0 Kostas Aslanidis over 6 years ago in reply to ERNESTO GALIANO

TI__Intellectual 2885 points

Hi Ernesto,
thanks for the response.
I will close that thread now, but feel free to contact us if you have nay further questions.

Regards
Kostas

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CCS/MSP430G2553: Dispersion between MSP430G2553 units in capacitance measurement