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Ematic
Associate II
June 18, 2025
Question

Configure LoRa E22-900M22s module and MAX3485 (for Rs485) into STM32H753ZIT6

  • June 18, 2025
  • 1 reply
  • 1659 views

Hi, I am working on configuring LoRa (E22-900M22S) and the MAX3485 transceiver to establish RS-485 communication using the STM32H753ZI. I have connected the LoRa and MAX3485 modules as per the following reference:

LoRa(E22-900M22S)
LoRa Pin STM32H753ZI Pin (example)
MOSI  PA7 (SPI1_MOSI)
MISO  PA6 (SPI1_MISO)
SCK  PA5 (SPI1_SCK)
NSS  PA4 (GPIO)
RESET  PB0 (GPIO)
DIO1  PB1 (EXTI-capable GPIO)
DIO2 PB2 (EXTI-capable GPIO)
BUSY  PB10 (GPIO input)
GND GND
VCC 3.3V

 

RS-485(MAX3485)
STM32H753ZI Pin MAX3485 Pin
PD8 DI
PD9 RO
PD12 (or any GPIO with DE support) DE + RE (tied together)
3.3V VCC
GND GND

Could you please guide me on how to configure both LoRa and RS-485 communication using STM32CubeIDE?

1 reply

Andrew Neil
Andrew Neil
Super User
June 18, 2025

A schematic is a better way to present an electronic circuit.

I'm not clear if you mean that the H7 is connected to the E22 LoRa via RS485, or if these are two separate interfaces?

A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
E
EmaticAuthor
Associate II
June 19, 2025

Hi @Andrew Neil, in response to your concern, I’ve shared the schematic diagram. Please note that the E22 LoRa and MAX485 (RS485) modules are separate interfaces.

 

Andrew Neil
Andrew Neil
Super User
June 19, 2025

You've marked by previous reply as The Solution - but it was really just a question.

Are you saying that you've now resolved the problem?

If not, here are instructions to un-mark it.

 

@Ematic wrote:

the E22 LoRa and MAX485 (RS485) modules are separate interfaces.

So just handle them separately:

  1. the E22 LoRa does not depend on the RS485 - it's just the same as any other E22 LoRa application
     
  2. the RS485 does not depend on the E22 LoRa - it's just the same as any other RS485 application

 

Note that the E22 is a third-party product - not ST - so you should go to Ebyte for support with that: 

https://www.cdebyte.com/products/E22-900M22S

 

A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
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