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Wave generate using PSoC? | Cypress Semiconductor

Wave generate using PSoC?

Summary: 4 Replies, Latest post by danaaknight on 30 Mar 2013 05:17 AM PDT
Verified Answers: 0
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stabomfalcon's picture
User
2 posts

 

Hi there.

 

How do I use the analog out pins of PSoC to generate waves, say triangle wave etc?

 

Arvind Krishnan's picture
Cypress Employee
143 posts

 

 

PSoC 1 has a digital to analog converter (DAC) which can be used for this.

 

A good place to start would be this application note - AN2025 - Analog – Sine Wave Generation with PSoC® 1

 

The first example project shows how you can define your waveform using a lookup table, and then feed it to the DAC to generate a scaled, proportional analog voltage.

 

 

 

 

 

 

stabomfalcon's picture
User
2 posts

 

Thanks for the suggestions. With the WaveDAC or VDAC, the output range is limited to 0 to 4.080V. Is there something internal to PSoC which can scale to 5V like a PGA?

 Otherwise I might go with the PSoC 1 approach, simple 8 bit DAC updates.

user_14586677's picture
User
7646 posts

The PSOC III PGA is rated to swing to 150 mV of either rail with a 100K ohm load.

 

An alternative approach is to use an integrator approach, step response of an integrator

is a ramp. Note in PSOC 1 the output buffer does not have R-R performance either.

Use of an integrator can give you more linearity, and with a simple AGC loop will handle

different frequencies to yield a constant amplitude output. Additionally should be able

to achieve higher frequencies than with DAC/LUT approach. The only significant downside

would be lowest ramp rate achievable due to leakage.

 

Regards, Dana.

 

 

user_14586677's picture
User
7646 posts

The prior post has severe limits on frequency output, LUT case, < 1 Khz for 64 bit LUT.

 

Alternatives -

 

1) Use BPF and feed it with a square wave, you can get 100 Khz like performance.

Limitation is tuning BPF, calculations and register writes needed to do this. And

limits on low frequencies obtainable.

 

2) PSOC 3/5 Wavedac component. www.cypress.com/

 

www.element14.com/community/docs/DOC-48063/l/cypress-ce56171--training-document-on-sine-wave-generator-with-dac-for-psoc-3-and-psoc-5-family

 

3) External DDS, DC to 100 Mhz +. www.psocdeveloper.com/.../an-pointer/​an2380/an-file/​an2380.pdf.html

 

Regards, Dana.

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