Add BMP280/BME280 (tested only on BME); add SHT3x (bug: reads only once)

I2Csensors/PCA9548

@@ -1,16 +1,14 @@
 #!/bin/bash
 
 if [[ $# != 1 || $((-(-$1))) != $1 ]]; then
-	echo "Usage: $0 cnannel" >&2
+	echo "Usage: $0 cnannel [!0-7 == all off]" >&2
 	exit 1
 fi
 
-if [[ $1 < 0 || $1 > 7 ]]; then
-	echo "Channel number should be from 0 to 7" >&2
-	exit 1
-fi
+CMD="0"
+[[ $1 -ge 0 && $1 -le 7 ]] && CMD=$((1 << $1))
 
-echo $((1 << $1))
+echo "send $CMD"
 
-i2ctransfer -y 6 w1@0x70 $((1 << $1))
-i2cdetect -y -r 6
+i2ctransfer -y 6 w1@0x70 $CMD
+i2cdetect -y -r 6