MCUMGR remote firmware update

[AngusKu]

| Host |  <---- UART ----> | nRF52833 (central) |  <-- BLE--> | nRF52833 (Target) |

I have a requirement where I hope to update the central's firmware image through the Host.
However, I also want the Host to be able to update the firmware image of the target through the central.

As a beginner, I'm currently unsure how to proceed.

From what I understand, it seems possible to enable MCUMGR functionality on the Zephyr running on the central.
But I'm not sure how firmware updates can be performed between the central and target.

Which nordic zephyr examples can I refer to?
or suggestions regarding this design architecture?

[Vidar Berg]

Hello,

You can integrate the GATT DFU SMP Service Client on your GAP central as demonstrated by the Bluetooth: Central SMP Client sample. Unfortunately, there are not official samples that implements DFU support. You may have a look at this example for that: https://github.com/simon-iversen/ncs_samples/tree/master/central_smp_client_dfu 

Best regards,

Vidar

[AngusKu]

I would like to ask a question about the DFU SMP service.

In dfu_smp.c ,
Why does bt_dfu_smp_command invokes bt_gatt_write_without_response ?

	/* Send request */
	ret = bt_gatt_write_without_response(dfu_smp->conn,
					     dfu_smp->handles.smp,
					     cmd_data,
					     cmd_size,
					     false);
	if (ret) {
		dfu_smp->cbs.rsp_part = NULL;
	}

How can we ensure that the SMP server receives every data packet sent by the Central during image upload?

[Vidar Berg]

You will get a image upload response for each chunk of data you send through the image upload request command: https://docs.nordicsemi.com/bundle/ncs-latest/page/zephyr/services/device_mgmt/smp_groups/smp_group_1.html#image_upload_response.  

[AngusKu]

Thanks for sharing this information.

Due to our need for relay functionality,
I have been recently referencing the uart_mcumgr.c implementation in the Nordic Zephyr SDK.

I would like to ask under what circumstances one would choose the CONFIG_MCUMGR_SMP_UART_ASYNC option?"

[Vidar Berg]

This setting allows you to use the Asynchronous API instead of the Interrupt-driven API in the mcumgr driver. The async UART driver provides better utilization of the DMA feature at the cost of increased memory usage. It can make the data reception more reliable when you don't use hardware flow control.