Very slow performance using LPUART

RE: Very slow performance using LPUART

GiulianoFranchetto — Thu, 26 Oct 2023 09:38:20 GMT

Hi Sigurd,

I think I've found where the problem was. In an old piece of code, we were using uart_poll_out() function which sends 1 byte after the other, inducing A LOT of REQ/RDY negociations (and a lot of time).

We've changed all the uart_poll_out() calls to fifo_fill() and the problem seems to be fixed.

I'll do more testing today

Giuliano

RE: Very slow performance using LPUART

GiulianoFranchetto — Thu, 26 Oct 2023 09:22:22 GMT

If it can help you, here is the logs for:

The receiver:

[00:02:41.805,236] <dbg> lpuart: uart_callback: RX: Ready buf:0x200070ac, offset: 0,len: 1
[00:02:41.805,664] <dbg> lpuart: uart_callback: Rx buf released
[00:02:41.805,969] <dbg> lpuart: uart_callback: Rx disabled
[00:02:41.806,274] <dbg> lpuart: api_rx_buf_rsp: buf rsp, state:5
[00:02:41.806,610] <dbg> lpuart: rdy_pin_handler: RX: Request detected.
[00:02:41.806,915] <dbg> lpuart: activate_rx: RX: Ready
[00:02:41.808,135] <dbg> lpuart: rdy_pin_handler: RX: End detected.
[00:02:41.808,990] <dbg> lpuart: uart_callback: RX: Ready buf:0x200070ac, offset: 0,len: 1
[00:02:41.809,417] <dbg> lpuart: uart_callback: Rx buf released
[00:02:41.809,722] <dbg> lpuart: uart_callback: Rx disabled
[00:02:41.810,028] <dbg> lpuart: api_rx_buf_rsp: buf rsp, state:5
[00:02:41.810,363] <dbg> lpuart: rdy_pin_handler: RX: Request detected.
[00:02:4[00:02:41.826,965] <dbg> lpuart: rdy_pin_handler: RX: End detected.
[00:02:41.832,824] <dbg> lpuart: uart_callback: RX: Ready buf:0x200070ac, offset: 0,len: 1
[00:02:41.833,251] <dbg> lpuart: uart_callback: Rx buf released
[00:02:41.833,587] <dbg> lpuart: uart_callback: Rx disabled
[00:02:41.833,862] <dbg> lpuart: api_rx_buf_rsp: buf rsp, state:5
[00:02:41.834,197] <dbg> lpuart: rdy_pin_handler: RX: Request detected.
[00:02:41.834,503] <dbg> lpuart: activate_rx: RX: Ready
[00:02:41.835,754] <dbg> lpuart: rdy_pin_handler: RX: End detected.
[00:02:41.836,578] <dbg> lpuart: uart_callback: RX: Ready buf:0x200070ac, offset: 0,len: 1
[00:02:41.837,036] <dbg> lpuart: uart_callback: Rx buf released
[00:02:41.837,341] <dbg> lpuart: uart_callback: Rx disabled

The sender:

[00:02:41.329,162] <dbg> lpuart: api_tx: tx len:1
[00:02:41.336,395] <dbg> lpuart: req_pin_handler: TX: Confirmed, starting.
[00:02:41.336,944] <dbg> lpuart: tx_complete: TX completed, pin idle
[00:02:41.337,371] <dbg> lpuart: api_tx: tx len:1
[00:02:41.355,255] <dbg> lpuart: req_pin_handler: TX: Confirmed, starting.
[00:02:41.355,773] <dbg> lpuart: tx_complete: TX completed, pin idle
[00:02:41.356,201] <dbg> lpuart: api_tx: tx len:1
[00:02:41.359,008] <dbg> lpuart: req_pin_handler: TX: Confirmed, starting.
[00:02:41.359,527] <dbg> lpuart: tx_complete: TX completed, pin idle
[00:02:41.359,985] <dbg> lpuart: api_tx: tx len:1
[00:02:41.382,873] <dbg> lpuart: req_pin_handler: TX: Confirmed, starting.
[00:02:41.383,392] <dbg> lpuart: tx_complete: TX completed, pin idle
[00:02:41.383,850] <dbg> lpuart: api_tx: tx len:1
[00:02:41.386,627] <dbg> lpuart: req_pin_handler: TX: Confirmed, starting.
[00:02:41.387,145] <dbg> lpuart: tx_complete: TX completed, pin idle
[00:02:41.387,573] <dbg> lpuart: api_tx: tx len:1
[00:02:41.410,461] <dbg> lpuart: req_pin_handler: TX: Confirmed, starting.
[00:02:41.410,980] <dbg> lpuart: tx_complete: TX completed, pin idle
[00:02:41.411,468] <dbg> lpuart: api_tx: tx len:1
[00:02:41.414,215] <dbg> lpuart: req_pin_handler: TX: Confirmed, starting.
[00:02:41.414,764] <dbg> lpuart: tx_complete: TX completed, pin idle
[00:02:41.415,191] <dbg> lpuart: api_tx: tx len:1

It seems that the bytes are sent in packet on 1. Would it explain why it takes so much time?

Is it possible to send multiple bytes between each REQ/RDY cycle, to reduce overhead?

RE: Very slow performance using LPUART

GiulianoFranchetto — Thu, 26 Oct 2023 08:57:05 GMT

Hi Sigurd,

Sorry for the delay. I've tried to use this kconfig option, but nothing changes.

It still takes approx. 4 seconds to send 2kb of data between both core using LPUART.

What should I try next?

Regards

RE: Very slow performance using LPUART

Sigurd — Mon, 25 Sep 2023 10:50:33 GMT

Did you try with CONFIG_NRF_SW_LPUART_HFXO_ON_RX=n ?

RE: Very slow performance using LPUART

GiulianoFranchetto — Mon, 25 Sep 2023 08:19:34 GMT

Hi Sigurd,

Any news on that subject?

RE: Very slow performance using LPUART

Sigurd — Thu, 07 Sep 2023 14:58:53 GMT

I guess that also depends on how many packets you are sending. Turning on HFXO prolongs receiver activation for up to 3 milliseconds.

RE: Very slow performance using LPUART

GiulianoFranchetto — Thu, 07 Sep 2023 13:56:38 GMT

Would it explain the overall slow transfer, even in case of big packets?

RE: Very slow performance using LPUART

Sigurd — Thu, 07 Sep 2023 13:51:04 GMT

Hi!

I checked with the developer. One of the main reasons might be CONFIG_NRF_SW_LPUART_HFXO_ON_RX which by default is on. It turns on HFXO before every RX transfer. Usually that can be turned off. Other thing is that RX packet is reported after receiving RXTO event (UARTE being turned off). This event is generated 5 bytes time after end of packet. So if 1 byte packet is send it will take approx time needed to transfer >6 byte. So there will be noticeable overhead when there are short packets.

RE: Very slow performance using LPUART

GiulianoFranchetto — Thu, 07 Sep 2023 07:21:19 GMT

Hi Sigurd.

Any news or idea on that issue?

Giuliano

RE: Very slow performance using LPUART

GiulianoFranchetto — Tue, 05 Sep 2023 13:24:59 GMT

1/ We send a lot of smaller packets (between 20 and 100 bytes approx.), and sometimes big ones

2/ Yes, I changed both overlay.

RE: Very slow performance using LPUART

Sigurd — Tue, 05 Sep 2023 13:22:19 GMT

1) Are you sending 2100 bytes packets, or smaller ones as well?

2) Did you set the baudrate to 1000000 for both the nRF9160 and the nRF5340?

RE: Very slow performance using LPUART

GiulianoFranchetto — Tue, 05 Sep 2023 13:12:17 GMT

Increasing the baudrate does not resolve the issue (it may even be a bit worse, not really sure)

RE: Very slow performance using LPUART

GiulianoFranchetto — Tue, 05 Sep 2023 13:00:31 GMT

No error.

The messages are received.

I'll try the baudrate right away

RE: Very slow performance using LPUART

Sigurd — Tue, 05 Sep 2023 12:43:25 GMT

Hi,

[quote userid="16133" url="~/f/nordic-q-a/103464/very-slow-performance-using-lpuart"]We would need to be able to send/receive packets of at least 2100 bytes.[/quote]

Are you getting any errors when doing that? or is only only a bit slow?

[quote userid="16133" url="~/f/nordic-q-a/103464/very-slow-performance-using-lpuart"] current-speed = <115200>;[/quote]

Could you try this ?

   baudrate = <1000000>;