RE: PLC Module
I'm waiting for a response supplier via vendor, who assures me that the supplier says it should work as it is and that I don't need RTS. I pointed out that the ESP-IDF documentation for UART indicates that RS485 Half Duplex requires a RTS pin (https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/uart.html):
I think I'm going to have to tie a wire between the DE pin on the 3485 to a free GPIO to get the functionality I need.
Hopefully the supplier will eventually provide some official documentation or schematics. I suspect that this might be what you get.
Is anyone from M5Stack here?
RE: PLC Module
Looks like the 485 driver is a Exar SP3485.
Some vendor on Alibaba claims it is max3485esa replacement.
The SP3485 chip has
Pin 1 - RO - Receiver output
Pin 2 - RE - Receiver Output Enable Active LOW
Pin 3 - DE - Driver Output Enable Active HIGH
Pin 4 - DI - Driver Input
Pin 5 - GND - Ground Connection
Pin 6 - A - Non-Inverting Driver Output/Receiver Input
Pin 7 - B - Inverting Driver Output/Receiver Input
Pin 8 - Vcc - Positive Supply
What pin is DE - Driver enable?
Pin 1 - RO -> G16
Pin 2 - RE -> ???
Pin 3 - DE -> ???
Pin 4 - DI -> G17
Pin 5 - GND -> (output port G)
Pin 6 - A -> (output port A)
Pin 7 - B -> (output port B)
Pin 8 - Vcc - 5V (?)
Is there a schematic for the little module?
I am converting a project from a raw esp32 module/MAX 485 driver -> modbus to M5Stack/PLC module.
Does the PLC module supply power to the CPU from the 24V input?
Is there an RTS Control line for the RS485 converter or is RTS Control automatic?
(RTS Control is a method with which the RS232 device (typically a PC) tells an RS232-RS485 converter when it should enable its RS485 driver, i.e. when it should be transmitting. http://www.kksystems.com/rtscontrol )
Is there a chip specification for the 485 converter? Which is used?