HCI UART

[Christoffer Brask]

Hi, 

I'm trying to use the HCI UART sample to provide Bluetooth support through UART. At first I want to test it between two Nordic Boards, but later switch to another MCU.

One first nRF52840 DK I have flashed the HCI UART sample.

One the second nRF52840 DK I have flashed a peripheral_hr sample and added the the required configs:

CONFIG_BT_HCI=y

CONFIG_BT_LL_SW_SPLIT=n

I have also created an overlay file for the peripheral_hr build

/ {
	chosen {
		zephyr,bt-hci = &uart1;
	};
};

&uart1
{
	current-speed = <1000000>;
	hw-flow-control;
	status = "okay";

    bt_hci_uart: bt_hci_uart {
		compatible = "zephyr,bt-hci-uart";
		status = "okay";
	};
};
&uart1_default {
	group2 {
		psels = <NRF_PSEL(UART_RX, 1, 1)>,
				<NRF_PSEL(UART_TX, 1, 2)>,
				<NRF_PSEL(UART_RTS, 1, 3)>,
				<NRF_PSEL(UART_CTS, 1, 4)>;
	};
};

I have connected UART0 from nRF52840 DK (HCI UART) to UART1 from nRF52840 (peripheral_hr)

RTS (0.05) -> CTS (P1.04)

TX (P0.06) -> RX (P1.01)

CTS (P0.07) -> RTS (P1.03)

RX (P0.08) -> TX (1.02)

GND -> GND

When testing I receive the error "HCI driver open failed (-1)" which comes from uarte_nrfx_poll_in, more specific from

if (!nrf_uarte_event_check(uarte, NRF_UARTE_EVENT_ENDRX)) {

        return -1;

    }

Do you have any idea why the input buffer is always empty?

Do the nRF52840 DK (peripheral_hr) need to be able to reset the nRF52840 DK (hci_uart)?

I assume I should not add the overlay-all-bt_ll_sw_split.conf when building the HCI UART sample?

Best regards,

Christoffer

[Sigurd]

Hi!

RTS (0.05) -> CTS (P1.04)

TX (P0.06) -> RX (P1.01)

CTS (P0.07) -> RTS (P1.03)

RX (P0.08) -> TX (1.02)

Pin 5,6,7,8 is connected to the interface MCU. I suggest using some different pins for HCI.

https://docs.nordicsemi.com/bundle/ug_nrf52840_dk/page/UG/dk/vir_com_port.html

[Christoffer Brask]

I should have added that I have already tried that, changing the overlay file for the nRF52840 (hci_uart) to use UART1..

[Sigurd]

Christoffer Brask said:

I should have added that I have already tried that, changing the overlay file for the nRF52840 (hci_uart) to use UART1..

So what pins are you using now?

Do the nRF52840 DK (peripheral_hr) need to be able to reset the nRF52840 DK (hci_uart)?

That would be more robust. We do that on the nRF9160-DK (where on-board nRF52840 can be used as a BLE Controller, and the BLE host can run on the nRF9160):

https://github.com/nrfconnect/sdk-zephyr/blob/main/boards/nordic/nrf9160dk/nrf52840_reset.c

https://github.com/nrfconnect/sdk-zephyr/blob/main/boards/nordic/nrf9160dk/nrf9160dk_nrf9160_common_0_14_0.dtsi#L20

https://github.com/nrfconnect/sdk-zephyr/blob/main/boards/nordic/nrf9160dk/dts/bindings/nordic%2Cnrf9160dk-nrf52840-reset.yaml

On the device that is the BLE host, set these:

CONFIG_BT=y
CONFIG_BT_HCI=y
CONFIG_BT_CTLR=n
CONFIG_BT_WAIT_NOP=y

I assume I should not add the overlay-all-bt_ll_sw_split.conf when building the HCI UART sample?

Correct, don't use overlay-all-bt_ll_sw_split.conf

[Christoffer Brask]

Hi Siguard,

Thanks so far 

HCI                   HOST

RTS (1.03) -> CTS (P1.04)

TX (P1.02) -> RX (P1.01)

CTS (P1.04) -> RTS (P1.03)

RX (P1.01) -> TX (1.02)

I have tried adding the configs to the peripheral_hr prj.conf without any luck.

I also started playing with the reset but couldn't get bt_hci_transport_setup to be called. I assume it is called from h4_open?

From what I hear the reset shouldn't be entirely necessary, so maybe we shouldn't put to much focus on that?

[Sigurd]

Hi! You should place RX and CTS , and TX and RTS, in different groups. (RX and CTS group need bias-pull-up)

See this overlay:

	uart1_default: uart1_default {
		group1 {
			psels = <NRF_PSEL(UART_RX, 1, 1)>;
			        <NRF_PSEL(UART_CTS, 1, 4)>;
			bias-pull-up;
		};
		group2 {
			psels = <NRF_PSEL(UART_TX, 1, 2)>;
			        <NRF_PSEL(UART_RTS, 1, 3)>;
		};
	};