<![CDATA[Modbus Master crashes and missing documentation]]>Hi,
I am trying to create a modbus master application in micropython. I cannot figure out how to use the write_single_coil register as I get a ValueError: Illegal coil value when using following line:
modbus.write_single_coil(1,0, 1, timeout=500)

Also, the documentation on Modbus is really flaky - can you point to some examples or maybe the source code of the implementation so I can look it up?

]]>https://community.m5stack.com/topic/5401/modbus-master-crashes-and-missing-documentationRSS for NodeTue, 28 Apr 2026 23:52:33 GMTTue, 20 Jun 2023 22:17:10 GMT60<![CDATA[Reply to Modbus Master crashes and missing documentation on Thu, 06 Jul 2023 07:45:17 GMT]]>Hi, @insaneLX 0_1688369025206_5545b634-1765-460d-a5c1-c3d1ae46fd74-image.png
0xff00(ON or 1) and 0x00(OFF or 0)

]]>https://community.m5stack.com/post/21464https://community.m5stack.com/post/21464Thu, 06 Jul 2023 07:45:17 GMT<![CDATA[Reply to Modbus Master crashes and missing documentation on Thu, 29 Jun 2023 22:20:04 GMT]]>A list it is!

try:
ret = modbus.write_multiple_coils(comms.DEVICE_ADDRESS, 0,(
sig.smoke_flap,
sig.transport,
sig.ignition,
sig.smoke_fan,
sig.extinguish,
sig.flood,
sig.ember_air,
sig.alarm
), timeout=200)

works nicely.

]]>https://community.m5stack.com/post/21400https://community.m5stack.com/post/21400Thu, 29 Jun 2023 22:20:04 GMT<![CDATA[Reply to Modbus Master crashes and missing documentation on Thu, 22 Jun 2023 21:33:30 GMT]]>Hello @insaneLX

I think the multiple coils function takes a list, but it didn't work for me either.

Thanks
Felix

]]>https://community.m5stack.com/post/21274https://community.m5stack.com/post/21274Thu, 22 Jun 2023 21:33:30 GMT<![CDATA[Reply to Modbus Master crashes and missing documentation on Wed, 21 Jun 2023 16:43:57 GMT]]>Felix, thanks for the reply.
I was trying to use the write_single_coil as workaround. I wanted to use the write multiple coils function. But it does not have a parameter to set the number of coils to be written and the documentation is less than complete. Any ideas? How does the system know what to write?

]]>https://community.m5stack.com/post/21258https://community.m5stack.com/post/21258Wed, 21 Jun 2023 16:43:57 GMT<![CDATA[Reply to Modbus Master crashes and missing documentation on Wed, 21 Jun 2023 06:42:27 GMT]]>Hello @insaneLX

from earlier posts I assume you're trying with an M5Tough, correct?

Well, I can confirm that write_single_coil fails with Value Error as soon as the value is different from 0.

So, yes, I'd say it is broken. @m5stack could you please look into that. Thanks.

BTW: other Modbus blocks like write_single_register work for me.

Thanks
Felix

]]>https://community.m5stack.com/post/21246https://community.m5stack.com/post/21246Wed, 21 Jun 2023 06:42:27 GMT