<![CDATA[UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104]]>Hi would like to use the COMMU module for RS485 interface in particular using the SP3485 tranceiver on UART 0 so GPIO 1 and 3 (M5 bus pin 13 and 14)

0_1557829991509_4ce5a99c-28ed-4d77-bcbe-a7abdb8e1116-image.png

Checking the M5stack basic core schematic seems same GPIO are used for communication with USB serial dirver CP2104

0_1557830032014_329232a5-8a78-4d9d-ae65-56f466075baa-image.png

Is there any possible conflict case ? can I use freely GPIO 1 & 3 on the bus or there is any constraints due to sharing with CP2104 ??

thanks for any clarification

Davide

]]>https://community.m5stack.com/topic/999/uart0-gpio1-3-usage-for-rs485-and-possible-conflict-with-cp2104RSS for NodeWed, 29 Apr 2026 04:56:41 GMTTue, 14 May 2019 10:34:16 GMT60<![CDATA[Reply to UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104 on Thu, 16 May 2019 08:10:35 GMT]]>I share m5 support answer on the topic

"UART0 is a specifically assigned for log print, it is encapsulated by ESP32 at lower layer. It will print the system log automatically and seems like we users are not permitted to shut it down, so we don’t recommend users to use UART0 as a normal UART series port, it will interrupt you communication. That why we connect it with CP2104."

to me it's clear the usage of UART0 ..less cleare why this two GPIO are routed to the M5bus since can't be used

I will use UART2 for my custom project with this assignment GPIO34=RX GPIO17=TX

Davide

]]>https://community.m5stack.com/post/4299https://community.m5stack.com/post/4299Thu, 16 May 2019 08:10:35 GMT<![CDATA[Reply to UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104 on Wed, 15 May 2019 04:29:10 GMT]]>@arzaman said in UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104:

also in my mind is an issue ...
is possibile that 2 GPIO of the UART0 routed on the core bus are not usable at all ??

Davide

Sorry I missunderstood this comment.

]]>https://community.m5stack.com/post/4283https://community.m5stack.com/post/4283Wed, 15 May 2019 04:29:10 GMT<![CDATA[Reply to UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104 on Tue, 14 May 2019 22:39:39 GMT]]>@ajb2k3 I was referring to GPIO 1 & 3 that can't be used...

]]>https://community.m5stack.com/post/4281https://community.m5stack.com/post/4281Tue, 14 May 2019 22:39:39 GMT<![CDATA[Reply to UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104 on Tue, 14 May 2019 19:26:30 GMT]]>@arzaman GPIO2 is on the bus connector pin 19.

]]>https://community.m5stack.com/post/4280https://community.m5stack.com/post/4280Tue, 14 May 2019 19:26:30 GMT<![CDATA[Reply to UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104 on Tue, 14 May 2019 18:51:22 GMT]]>also in my mind is an issue ...
is possibile that 2 GPIO of the UART0 routed on the core bus are not usable at all ??

Davide

]]>https://community.m5stack.com/post/4279https://community.m5stack.com/post/4279Tue, 14 May 2019 18:51:22 GMT<![CDATA[Reply to UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104 on Tue, 14 May 2019 18:23:18 GMT]]>Hmn, that is an issue.
I wonder if a UART switcher/multiplexer could be of use to you in this case.

]]>https://community.m5stack.com/post/4278https://community.m5stack.com/post/4278Tue, 14 May 2019 18:23:18 GMT<![CDATA[Reply to UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104 on Tue, 14 May 2019 13:03:36 GMT]]>@ajb2k3 Unluckily the use of UART2 is NOT an option in my custom circuit since GPIO 16&17 are already used by another device

I think this is a "general" m5stack core problem: how can I use GPIO 1&3 routed on the bus if they are already in use by the CP2104 ??

Especially GPIO3 that is an output od the USB to serial adapter
two useless bus pin ?

Davide

]]>https://community.m5stack.com/post/4277https://community.m5stack.com/post/4277Tue, 14 May 2019 13:03:36 GMT<![CDATA[Reply to UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104 on Tue, 14 May 2019 10:46:16 GMT]]>I think there was an issue report by another forum member but they fixed it by wiring the unit to the other port.

]]>https://community.m5stack.com/post/4276https://community.m5stack.com/post/4276Tue, 14 May 2019 10:46:16 GMT