STM32U5/H5: uart.read_until_idle() every second transfer also returns the prevoius data + new data.

[vDorst]

I make a repo to easy demostrate the issue: https://github.com/vDorst/uartdmabug

Setup: STM32 Development board (STM32H573I-DK) with STM32H573IIK3Q.
Connect USB cable to STLINK port. Used for debug (probe-rs) and VCP (virtual comport).
I used putty to connect VCP port with settings: 115200-8-n-1.
UART7 can also be used. In my project that was I first noticed this behaviour.

After reset, you see 'Hello!' in putty terminal.

If you slowly (1 key/sec) type 1 to 0 in putty you can observe this behavior

Putty ouput

Hello!

Got: 1
Got: 2
Got: 23
Got: 4
Got: 45
Got: 6
Got: 67
Got: 8
Got: 89
Got: 0

Probe-rs output:

# cargo run --release
   Compiling uartdmabug v0.1.0 (<snip>\\uartdmabug)
    Finished `release` profile [optimized + debuginfo] target(s) in 2.45s
     Running `probe-rs run --chip STM32H573IIKx --connect-under-reset target\thumbv8m.main-none-eabihf\release\uartdmabug`
      Erasing ✔ 100% [####################]  32.00 KiB @ 471.92 KiB/s (took 0s)
  Programming ✔ 100% [####################]  28.00 KiB @  82.02 KiB/s (took 0s)                                                                                                                                                                                        
     Finished in 0.41s
Start Init
0.000091 ERROR UART7: Zero size!
└─ uartdmabug::__mb_link_task_task::{async_fn#0} @ src\main.rs:43
0.000091 ERROR UART1: Zero size!
└─ uartdmabug::__mb_link_task_task::{async_fn#0} @ src\main.rs:43
UART1: Got: n_bytes 1 data: [31]
UART1: Got: n_bytes 1 data: [32]
UART1: Got: n_bytes 2 data: [32, 33]
UART1: Got: n_bytes 1 data: [34]
UART1: Got: n_bytes 2 data: [34, 35]
UART1: Got: n_bytes 1 data: [36]
UART1: Got: n_bytes 2 data: [36, 37]
UART1: Got: n_bytes 1 data: [38]
UART1: Got: n_bytes 2 data: [38, 39]
UART1: Got: n_bytes 1 data: [30]

It is not only a single character but also has the same behavior with larger data.

If I parst ACBD, EFGH, IJLK as seperet groups into putty I got this output:

Putty ouput

Got: ACBD
Got: ACBDEFGH
Got: IJLK

Probe-rs output:

UART1: Got: n_bytes 4 data: [41, 43, 42, 44]
UART1: Got: n_bytes 8 data: [41, 43, 42, 44, 45, 46, 47, 48]
UART1: Got: n_bytes 4 data: [49, 4a, 4c, 4b]

I also tested this code on stm32u0 (arm thumbv6) and work fine.
But stm32u0 has a different DMA block.
So I think there is something wrong with the DMA setup.

I also noticed that:

• the first read_until_idle() always return Ok(0).
• First two transfers seems to be fine.

@Dirbaio you seems the initial author of the stm32u5 dma code.
Any idea?

-- update --
I saw that I mention STM32U5 but I tested it on a stm32H5.
But I also have a STM32 Development board (DK32U5G9J-DK1) with STM32U5G9NJH6Q at my desk.
I see same behaviour on stm32u5 as well.

[Dirbaio]

repo link is 404

[vDorst]

Fixed, was missing a g at the end