As discovered in the #10 (comment) and confirmed in the #10 (comment) , the card CLI (which is internally also used for the Python library) doesn't implement locking. This permits concurrent access to the card on I2C bus and potential garbage input states reporting. This manifest itself as cards inputs reported state constantly flapping, but only for the inputs which are currently set to high.
To reproduce this issue you can run multiple instances of the following script. The smaller is the sleep in the loop the higher is the chance for collision on the bus.
#!/bin/bash
declare -A INPUTS
INPUTS[1]=0
INPUTS[2]=0
INPUTS[3]=0
INPUTS[4]=0
INPUTS[5]=0
INPUTS[6]=0
INPUTS[7]=0
INPUTS[8]=0
INPUTS[9]=0
INPUTS[10]=0
INPUTS[11]=0
INPUTS[12]=0
INPUTS[13]=0
INPUTS[14]=0
INPUTS[15]=0
INPUTS[16]=0
declare -a KEYS
IFS=$'\n' KEYS=($(printf '%s\n' "${!INPUTS[@]}" | sort -n))
for ID in "${KEYS[@]}"
do
INPUTS[${ID}]=$(./16inpind 3 optrd ${ID})
echo "get initial input ${ID} : ${INPUTS[${ID}]}"
done
echo "--------------------------"
echo "start loop to detect input change"
while true
do
for ID in "${KEYS[@]}"
do
TMP=$(./16inpind 3 optrd ${ID})
if [ "${INPUTS[${ID}]}" -ne "${TMP}" ]
then
echo "Input: ${ID} changed from: ${INPUTS[${ID}]} to: ${TMP}"
INPUTS[${ID}]=${TMP}
fi
done
echo "-------"
sleep 0.1
done
Based on the proposed fix I would like to ask for the thread safe implementation of the library (Python calling popen, and Node-RED using the exec node).
As discovered in the #10 (comment) and confirmed in the #10 (comment) , the card CLI (which is internally also used for the Python library) doesn't implement locking. This permits concurrent access to the card on I2C bus and potential garbage input states reporting. This manifest itself as cards inputs reported state constantly flapping, but only for the inputs which are currently set to high.
To reproduce this issue you can run multiple instances of the following script. The smaller is the sleep in the loop the higher is the chance for collision on the bus.
Based on the proposed fix I would like to ask for the thread safe implementation of the library (Python calling popen, and Node-RED using the exec node).