Ubuntu server, 8 relay usb board need to turn on more than one at ounce

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I bought a china usb 8 relay switch board. It shows up in ubuntu server as a serial device. I figured out the commands to get it to work.

*Set Baud Rate of relay board

stty -F /dev/ttyUSB0 9600 -parity cs8 -cstopb

To start relay controller:

echo -e -n "\x50" > /dev/ttyUSB0

To activate relay for commands:

echo -e -n "\x51" > /dev/ttyUSB0

To turn on relay

echo -e -n "\x(number)" > /dev/ttyUSB0*

But my issue is if I turn on relay 1 (/x01) and then turn on relay 2 (/x02) relay 1 turns off. I'm trying to automate and will need it to turn on more than one relay at a time. I went thru with testers and started mapping each number, Like 03 turns on relay 01 and 02. But there has to be an easier way. Any help would be grateful.

scripting serial-port ubuntu shell bash
1 Answers

It is a bitwise control.

For example to turn on only port 0 (the first), you send \xFE.

(echo "obase=16" ; echo $((255 ^ 1)))|bc| sed -e 's/^/\\x/'
0xFE

Essentially take 255 and subtract these values for each port you wish to start: |Port|Number| |--| ---| |0|1| |1|2| |2|4| |3|8| |4|16| |5|32| |6|64| |7|128|

To turn relay 1, 4, 5, and 7 you need to send:

255 (all 8 bits stop)  - 2 (bit 1 start) - 16 (bit 4 start) - 128 (bit 7 start) = 109.

In hex 109 is 6D, so send \x6D to the device.

James Risner0
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