TTN Smart Sensor (Jeng-Iot)

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let shortPressTot = 0; let longPressTot = 0; let voltage = 0.00; function sflt162f(rawSflt16) { // rawSflt16 is the 2-byte number decoded from wherever; // it's in range 0..0xFFFF // bit 15 is the sign bit // bits 14..11 are the exponent // bits 10..0 are the the mantissa. Unlike IEEE format, // the msb is transmitted; this means that numbers // might not be normalized, but makes coding for // underflow easier. // As with IEEE format, negative zero is possible, so // we special-case that in hopes that JavaScript will // also cooperate. // // The result is a number in the open interval (-1.0, 1.0); // // throw away high bits for repeatability. rawSflt16 &= 0xFFFF; // special case minus zero: if (rawSflt16 == 0x8000) return -0.0; // extract the sign. var sSign = ((rawSflt16 & 0x8000) != 0) ? -1 : 1; // extract the exponent var exp1 = (rawSflt16 >> 11) & 0xF; // extract the "mantissa" (the fractional part) var mant1 = (rawSflt16 & 0x7FF) / 2048.0; // convert back to a floating point number. We hope // that Math.pow(2, k) is handled efficiently by // the JS interpreter! If this is time critical code, // you can replace by a suitable shift and divide. var f_unscaled = sSign * mant1 * Math.pow(2, exp1 - 15); return f_unscaled; } function decodeUplink(input) { switch (input.fPort) { case 1: //fPort 1 is normal message shortPressTot = input.bytes[0] + (input.bytes[1] * 256); //The total shortpresses (2bytes) longPressTot = input.bytes[2] + (input.bytes[3] * 256); //The total longpresses (2bytes) /*reserved bytes */ //2 bytes reserved for future use voltage = sflt162f(input.bytes[6]+(input.bytes[7]*256)) * 10; //voltage is saved as 2byte float. Multiply by 10 to get node votlage. return { data: { shortPressTot, longPressTot, voltage }, warnings: [], errors: [] }; case 2: //fPort 2 is heartbeat. This is decoded the same as a normal message shortPressTot = input.bytes[0] + (input.bytes[1] * 256); //The total shortpresses (2bytes) longPressTot = input.bytes[2] + (input.bytes[3] * 256); //The total longpresses (2bytes) /*reserved bytes */ //2 bytes reserved for future use voltage = sflt162f(input.bytes[6]+(input.bytes[7]*256)) * 10; //voltage is saved as 2byte float. Multiply by 10 to get node votlage. return { data: { shortPressTot, longPressTot, voltage }, warnings: [], errors: [] }; default: return { data: { }, warnings: ["usupported fPort"], errors: [] }; } }