Tag Archives: ds2482s

How to make the 1-wire bus more reliable on a Raspberry Pi

Thermal sensors, such as DS18B20 can be connected to the Raspberry Pi via 1-wire bus. However, the 1-wire bus is not implemented in hardware, but only as software emulation on GPIO4, which has some major disadvantages. The 1-wire data link is acting as a very long “antenna” which catches interferences. All GPIO pins of a Raspberry Pi are directly connected to the CPU. So every interference cought on 1-wire bus is transported directly to the Broadcom SoC. Furthermore, the 1-wire protocol needs a very tight and time-critical signal generation, so it’s resource-consuming to communicate with 1-wire slaves and therefore highly unreliable if running on a non-real-time operating system.
I noticed that the DS18B20 sensors, which I have wired to my Raspberry, return at least once or twice a day bad temerature values, making it impossible to retrieve reliable max/min temperature data.
I recently stumbled upon a DS2482S-100 1-wire master breakout board that allows to control one or many 1-wire slave devices by simply sending I2C commands, relieving the task of generating the time-critical signals the 1-wire protocol requires. It provides bidirectional protocol conversion between an I2C master and 1-wire slave devices. The breakout board makes use of a DS2482S-100 converter, that is exclusively sold in a SO-8 package which doesn’t fit onto a breadboard.

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