UART0 (GPIO1,3) usage for RS485 and possible conflict with CP2104

[arzaman]

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)

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

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

[ajb2k3]

I think there was an issue report by another forum member but they fixed it by wiring the unit to the other port.

[arzaman]

@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

[ajb2k3]

Hmn, that is an issue.
I wonder if a UART switcher/multiplexer could be of use to you in this case.

[arzaman]

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

[ajb2k3]

@arzaman GPIO2 is on the bus connector pin 19.

[arzaman]

@ajb2k3 I was referring to GPIO 1 & 3 that can't be used...

[ajb2k3]

@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.

[arzaman]

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