DFU error - Read no data from UART!

Question

nrfutil
dfu serial -pkg ble_ app _v1 .zip 
-p /dev/ttyUSB 0 - b 57600 - fc 1 
 When activating DFU sometimes on the last packet sent to the bootloader, I see "Read no data from UART!" 
 It works sometimes without error, but other times only on the last packet it generates the error below: 
 Sending firmware file... Selecting Object: type:2 Object selected: max_size:4096 offset:0 crc:0x00000000 Streaming Data: len:4096 offset:0 crc:0x00000000 Streaming Data: len:4096 offset:4096 crc:0xEE809E11 Streaming Data: len:4096 offset:8192 crc:0xF1152A96 Streaming Data: len:4096 offset:12288 crc:0x593512DF Streaming Data: len:4096 offset:16384 crc:0x6BCA54F6 Streaming Data: len:4096 offset:20480 crc:0xBDC1E7DF Streaming Data: len:4096 offset:24576 crc:0x6956F910 Streaming Data: len:4096 offset:28672 crc:0x97F8D1AB Streaming Data: len:4096 offset:32768 crc:0xF2803A78 Streaming Data: len:4096 offset:36864 crc:0x1C8CFAEA Streaming Data: len:4096 offset:40960 crc:0x1FDBF3C1 Streaming Data: len:4096 offset:45056 crc:0x9F553CB7 Streaming Data: len:4096 offset:49152 crc:0xA9804943 Streaming Data: len:4096 offset:53248 crc:0x0A96A50F Streaming Data: len:4096 offset:57344 crc:0x11BF809D Streaming Data: len:4096 offset:61440 crc:0x80204A23 Streaming Data: len:4096 offset:65536 crc:0xAF1D7F35 Streaming Data: len:464 offset:69632 crc:0x0756822C Read no data from UART! 
 Any ideas why the bootloader is not sending any response to the last packet in the DFU image? 
 nRF52832 
 SDK v15.3 
 S132 SoftDevice v6.1.1 
 PCA 10040

KSV · Accepted Answer

I was able to solve the issue. Here is what I observed and did: 1) Looking at the bootloader debug logging during the DFU, I see that the 4096 byte packets have the following occur after the 4K packet is sent: Host requests CRC on the last 4K packet and bootloader sends 0x3 response: nrf_dfu_req_handler: Handle NRF_DFU_OP_CRC_GET (data) nrf_dfu_req_handler: Offset:69632, CRC:0x0756822C nrf_dfu_req_handler: Request handling complete. Result: 0x1 nrf_dfu_serial: Sending Response: [0x3, 0x1] Then an OBJECT EXECUTE command is sent by the host and the bootloader immediately sends an 0x4 response: nrf_dfu_req_handler: Handle NRF_DFU_OP_OBJECT_EXECUTE (data) nrf_dfu_serial: Sending Response: [0x4, 0x1] 2) The last packet sent is less than 4K. In my case it is 464 bytes. On this part of the process I see the following: Host requests CRC on the last 464 byte packet and bootloader sends 0x3 response: nrf_dfu_req_handler: Handle NRF_DFU_OP_CRC_GET (data) nrf_dfu_req_handler: Offset:70096, CRC:0xA02E108B nrf_dfu_req_handler: Request handling complete. Result: 0x1 nrf_dfu_serial: Sending Response: [0x3, 0x1] Then an OBJECT EXECUTE command is sent by the host but this time the bootloader does not immediately send the 0x4 response: nrf_dfu_req_handler: Handle NRF_DFU_OP_OBJECT_EXECUTE (data) nrf_dfu_req_handler: Whole firmware image received. Postvalidating. nrf_dfu_validation: Hash verification. start address: 0x38000, size: 0x111D0 nrf_dfu_validation: Invalidating old application in bank 0. nrf_dfu_serial: Sending Response: [0x4, 0x1] Conclusion: The host side (nrfutil) does not wait long enough for the 0x4 response to be sent. Therefore it thinks there was no response (only at the end of the image) and although everything is fine on the bootloader side, the host side (nrfutil) gives the error message "Read no data from UART!" I have ported the nrfutil code into firmware and I added an extra delay at this "end of image" special case and the 0x4 response is received now and the error message is no longer generated.

KSV · Answer

BTW 
 Linux OS 
 Ubuntu 16.04.6 LTS 
 Application is: ble_app_uart_pca10040_s132 
 Bootloader is: secure_bootloader_uart_mbr_pca10040_debug

DFU error - Read no data from UART!

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