Firmware transfer over BLE for another MCU

Question

Hi, 
 
 We've a custom board which has NRF52832 and Maxime. They are connected over UART. ( I'm using ble_app_uart) 
 What I want is transfer binary data between Phone and nRF52 over BLE. Is there any application example? 
 After receiving binary data from Phone, we will store it to external EEPROM on our custom board, and doing Maxmie update further. 
 The binary data actually is for Maxime update. 
 
 I've tried using UART for transferring binary. 
 As I googled, TX characteristic of UART service(ble_app_uart) on Phone has 20 bytes payload, o ur binary file has about 4xx kbytes. 
 
 It takes too much time when nRF52 receive from Phone over UART and send binary over UART between 52832 soc and Maxime soc. 
 So maybe the better way is using BLE from Phone to nRF52. 
 
 I've read https://devzone.nordicsemi.com/f/nordic-q-a/29028/download-firmware-over-ble-for-another-mcu . Still confusing. 
 Is there application sample or guide for receiving data over BLE from Phone? Once nRF52 receives binary data, how to send binary packet over UART to Maxime. 
 
 Thanks. 
 Vick

Hung Bui · Accepted Answer

Hi Vick, 
 If you use NRF_DFU_SUPPORTS_EXTERNAL_APP = 1 the new image will be stored in bank 1 (right after the current application). After that the bootloader will simply switch to application. In your application you have full control of what you want to do with bank 1. In your application you can check in the boodloader setting if bank 1 is assigned this flag: 
 s_dfu_settings.bank_1.bank_code = NRF_DFU_BANK_VALID_EXT_APP; 
 Then you can start sending the image in bank 1 to the external IC. 
 Where do you find app_fifo_put () ? I'm not sure which application you are talking about ? Is it about UART communication ? If you have a look at app_uart_put() in app_uart_fifo.c you can define the number of bytes you want to put into the fifo.

Hung Bui · Answer

Hi Vick, Please be aware that the .zip file is not transferred via BLE. It's unzipped by the app on the phone (or nRFUtil/nRFConnect on PC) and only the init packet and the binary image is transferred. 
 I would suggest you to go for the option to implement the BLE receiving and forwarding on UART on the bootloader on the nRF52. And then implement a similar bootloader on the Maxime MCU that can also do verification and DFU update. Something similar to our UART DFU bootloader on the nRF5 SDK. Note that this is not a simple task and requires a deep understanding of the code of the bootloader. I would suggest you to get very familiar with the code of the bootloader.

Hung Bui · Answer

Hi Vick, 
 I don't fully understand what you are asking about. But this has nothing to do with NUS. 
 I suggest you to draw some figure to explain what you are planning to do. 
 For example: Phone |==BLE DFU==> nRF52 |===UART==> Maxime. 
 Then you can tell what exact you want to do on the nRF52 , on the Maxime etc. 
 
 What you are planning to make is complex and requires you to fully understand the code of the bootloader. You need to get very familiar with how the Bootloader works, how the DFU protocol is, how the UART DFU master works etc.

Firmware transfer over BLE for another MCU

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