Posts by sibrosan@mastodon.social
 (DIR) Post #B4k0JkFEBWkDnqcGVE by sibrosan@mastodon.social
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       @libreoffice Hi Neil!
       
 (DIR) Post #B5TnbhsFNOpzWwG4bQ by sibrosan@mastodon.social
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       @stux Look at them otting 🙂
       
 (DIR) Post #B5dv2vdgwphxIiydEW by sibrosan@mastodon.social
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       @The_Whore_of_Blahbylon Obama was much better than Trump at not being a rapist and a pedophile
       
 (DIR) Post #B5iUg4kjGv2Xt6ViMq by sibrosan@mastodon.social
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       @gutenberg_org I got hooked on Dickens after reading Robert Hughes' The Fatal Shore (about the history of Australia as a penal colony) which referred to this book, Great Expectations.I had associated Dickens with sugary Disney sentimentalism, but the historical realism and strong story telling in the actual books came as a revelation.I enjoyed this book a lot!
       
 (DIR) Post #B635KjAftn1gL1WpaC by sibrosan@mastodon.social
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       @gutenberg_org The giraffe of the family
       
 (DIR) Post #B8CJyAZSkSZyIkYVlI by sibrosan@mastodon.social
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       @tk do you have, beside termination resistors, failsafe bias resistors in place? Without the latter, the logic level received on the UART input, when the other side is not yet driving the RS-485 bus, might be low, and this might be interpreted by the UART as a 0 frame.https://www.analog.com/en/resources/technical-articles/rs485-cable-specification-guide--maxim-integrated.html
       
 (DIR) Post #B8CeWFr7bVxlcZLVlQ by sibrosan@mastodon.social
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       @tk 20kR is high, but the datasheet says the receiver has fail-safe feature so they may not even be necessary.Only the device at each end of the bus should have the termination resistor, remove it on any additional ones, see fig. 21 MAX485 should be powered by 5V but RPI is 3.3V logic so you should use a resistor divider on RO to protect it. You could try one with 1.8k and 3.3k. Input level on DE, DI, RE for high is >2.0V so they'd work with 3.3Vhttps://www.analog.com/media/en/technical-documentation/data-sheets/MAX1487-MAX491.pdfhope that helps
       
 (DIR) Post #B8CxqHKPjmUJ6nJD9c by sibrosan@mastodon.social
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       @tk Now an oscilloscope would be really handy to see what's going on 😉
       
 (DIR) Post #B8EuYA4PeKFJ4Ayf3Y by sibrosan@mastodon.social
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       @tk Aim for 750 ohms (total parallel) pull-ups and pull-downs to get 200 mV differential voltage (the maximum threshold voltage for the diff inputs) I remember this from a project I worked on ~40 years ago 🙄 Although the data sheet says the bias resistors are not needed, I guess that might be incorrect.
       
 (DIR) Post #B8GY8RKR3EAaO6inY0 by sibrosan@mastodon.social
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       @tk The original MAX485 was made by Maxim Integrated which was later acquired by Analog Devices.According to the AD product page, its MAX485 has "Short Circuit Current Limited DriverIntegrated Thermal ShutdownReceiver Fail-Safe for Input Open CircuitGuarantees Logic High"It sounds like the IC on this board has similar function to the original MAX485, but is in a number of ways not its equivalent...
       
 (DIR) Post #B8iq8KeRP9hIVtz1Q8 by sibrosan@mastodon.social
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       @gutenberg_org @DProofreaders Muito bom🙂