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Hello everyone , i am new here , i'm in an internship for the moment and i have been working on an iot project which serve on reading differents measurements from sdi-12 sensors with the EFM32 ship, the project i'm working on right now is the interface between uart pins tx and rx which give 3.3v and the sid12 which have one single data-line that uses inverted logic and it's levels are 5v and 0v .
**sdi-12 is a serial asynchroonous protocol at 1200 baud and contains 3 wires : gnd, 12v and serial-data-line.**
which means 3 problems occures :
-the conversion of 3.3 to 5v
-the inversion of this value, so for example we have logic high in tx (3.3v), in the data line it should be 0v which is logic high for sdi12 and vice-versa
-the bi-directionality, so when transmitting (tx==>data-line) and when recieving it should switch to (data-line==> rx) means put the tx pin in high-impedance state.
-all this a protection circuit should be added agaisnt short-circuits and high-voltages, also it should be working as an embeded module added to the main ship so it should be optimal.
i have created diffirents circuits for this and in general to solve the problems i used :
- a tri-state buffer SN74LVC1G240 to inverse and convert and also to switch to recieving mode by controlling the output with a gpio and put tx on high-impedance mode.
-the problem is i dont have good ideas for the protection like voltage-regulators and the protection against short-circuit that might occurs by the effect of 12V of the sdi-12-power-line. so can u tell me if the tri-state buffer is a good solution? and also help me with the proctection circuit? and thank u in advance
.
**sdi-12 is a serial asynchroonous protocol at 1200 baud and contains 3 wires : gnd, 12v and serial-data-line.**
which means 3 problems occures :
-the conversion of 3.3 to 5v
-the inversion of this value, so for example we have logic high in tx (3.3v), in the data line it should be 0v which is logic high for sdi12 and vice-versa
-the bi-directionality, so when transmitting (tx==>data-line) and when recieving it should switch to (data-line==> rx) means put the tx pin in high-impedance state.
-all this a protection circuit should be added agaisnt short-circuits and high-voltages, also it should be working as an embeded module added to the main ship so it should be optimal.
i have created diffirents circuits for this and in general to solve the problems i used :
- a tri-state buffer SN74LVC1G240 to inverse and convert and also to switch to recieving mode by controlling the output with a gpio and put tx on high-impedance mode.
-the problem is i dont have good ideas for the protection like voltage-regulators and the protection against short-circuit that might occurs by the effect of 12V of the sdi-12-power-line. so can u tell me if the tri-state buffer is a good solution? and also help me with the proctection circuit? and thank u in advance
.
