https://forge.codesys.com/forge/talk/Engineering/thread/bfcf6c02b2/2020-02-27T14:26:01.720000ZRecent posts to Very short pulse out2020-02-27T14:26:01.720000Z2020-02-27T14:26:01.720000Zlucaver89https://forge.codesys.com/u/lucaver89/https://forge.codesys.com83ea351f2d9ded14ef585149380d61679f575498

<div class="markdown_content"><p>Hi, </p> <p>The GPIO is made by a MCP23017 with i2c bus. If I remember well that's frequency rate is 100KHz for the pic microchip. I realy don't know if the i2c of the raspberry py works with the same frequency.</p> <p>Thanks<br/> Luca</p></div>

2020-02-27T14:26:01.289000Z2020-02-27T14:26:01.289000ZdFxhttps://forge.codesys.com/u/dfx/https://forge.codesys.coma58ec3a7b7c8ec98f37de77627c3061651f4c0b5

<div class="markdown_content"><p>To module PWM AC loads we usually make use of triac. Some can be controlled by bus, other by analog output and some by digital input.</p> <p>Does your spec about GPIOs refresh rate and output commutation rate are within 50µs ?</p></div>

2020-02-27T14:25:59.909000Z2020-02-27T14:25:59.909000Zlucaver89https://forge.codesys.com/u/lucaver89/https://forge.codesys.comd4839d6354b749e0b9c286d988fd7170bb0a211e

<div class="markdown_content"><p>Thank you for your answer. </p> <p>I'm thinking to use a microcontroller to module the pwm for AC loads. </p> <p>Thanks <br/> Luca</p></div>

2020-02-27T14:25:59.487000Z2020-02-27T14:25:59.487000ZdFxhttps://forge.codesys.com/u/dfx/https://forge.codesys.com9f24fd4eacd6e314a5567567a588c29c16e8a928

<div class="markdown_content"><p>50µs is extremely short for a PLC system (expected cycle times are generally tens of ms). Be sure your hardware can handle it.</p> <p>My bet would be a separate task with top priority with only refreshing your I/O value (ex: out := NOT out;).<br/> Don't forget to set the correct refresh to your I/O also.</p></div>

2020-02-27T14:25:59.053000Z2020-02-27T14:25:59.053000Zlucaver89https://forge.codesys.com/u/lucaver89/https://forge.codesys.comc98b19bf39f113448ccea7488a468d250aeacae5

<div class="markdown_content"><p>Hello to All,</p> <p>from gpio number 23 of my raspberry pi 3 I have to generate a impulsive clock by 50 uSend. I have a couples of ideas to do it, but unfortunatly I don't know which is the best way. The first idea is using a simple TP timer with preset time at 50uS. The second one is set a new task with cycle time at 50 uS. <br/> Could anyone help me please?</p> <p>Thank you<br/> luca</p></div>