more uart ports

[John Doe1]

Posted on July 06, 2017 at 21:02

Hi,

My stm32 board has four uart ports. Each of them is connected to rs 485 transmitter (tx only).

I'm looking for any ideas how to extend my project to have more than four uart ports - up to 10.

My first idea was to connect from my main stm32 board to many smaller stm32 boards over spi (one small board = one rs485) but I'm afraid of synchronization - i need to send all data to rs485 at the same time.

Do you have any other ideas?

I will be grateful for any ideas.

#synchronize #uart #rs485

[Tesla DeLorean]

Posted on July 06, 2017 at 21:47

Aren't there STM32 parts with 6 or more UART's?

A bunch of Quad-UART chips on an FSMC bus? Ones with some real FIFO depth.

Maxim has some SPI Quad-UART.

Not sure I'd use SPI, probably have a bunch of slave STM32 with multiple USART, with a higher bandwidth SLIP or CMUX serial link for a backbone.

[Andrei Chichak]

Posted on July 06, 2017 at 21:51

1. Co-processors on a CAN bus.
2. Switch to a powerPC chip with an eTPU and have 32 half uarts in microcode.
3. External UARTS but some of the SPI ones are a bitch to work with.
4. Bit bang a whole bunch of ports, or kill youself, it would be less painful.
5. Some old style quad uarts on something like the FMC bus with a bunch of chip selects and glue.
6. An FPGA with a bunch of half uarts, bus interface, and glue.

Just throwing things out there.

Andrei

[Tesla DeLorean]

Posted on July 06, 2017 at 23:03

>>External UARTS but some of the SPI ones are a ***** to work with.

Frequently the IC designers feeling about what is a good idea doesn't comport with everyone else's. It could be a customer design that the vendor gets to sell too.

[John Doe1]

Posted on July 06, 2017 at 23:08

Thanks for all replies.

Any ideas how to send different data through all uarts on the same time using CAN-bus/

SPI Quad-UART.?

[Andrei Chichak]

Posted on July 06, 2017 at 23:17

What do you mean by 'same'? Same time would indicate that you would be using a set of synchronous UARTs, all sharing a common external clock.

If you mean really close to the same, then that is completely different. Async but simultaneous is easy to do using interrupts or DMA. If you're polling, and you send out messages in a round-robin schedule, you're dead.

Andrei