Extending communication timeouts

[mateusz-holenko]

---

NOTE: I'm posting an issue in this repository because https://github.com/arduino/BOSSA does not allow to report issues and the bossac tool is directly used by Arduino IDE.

---

We are working on an integration of Arduino IDE and an external simulator (Renode, www.renode.io) and noticed SAM-BA operation failed errors when loading a binary on Linux using bossac.

In order to make the experience of using our simulator as close as possible to the actual hardware, we are exposing it as a USB device using the USB/IP stack and pretending that we are an Arduino board (Arduino Nano 33 BLE Sense to be exact). This way it's visible in the system as a physical USB device and the IDE can interact with it without even knowing it's a simulator.

Unfortunately we are noticing problems when handling bootloader commands that seem to be related to timeouts. On some systems loading fails with the following output:

Set binary mode
version()=Arduino Bootloader (SAM-BA extended) 2.0 [Arduino:IKXYZ]
Connected at 921600 baud
identifyChip()=nRF52840-QIAA
write(addr=0,size=0x34)
writeWord(addr=0x30,value=0x400)
writeWord(addr=0x20,value=0)
version()=Arduino Bootloader (SAM-BA extended) 2.0 [Arduino:IKXYZ]
Device       : nRF52840-QIAA
Version      : Arduino Bootloader (SAM-BA extended) 2.0 [Arduino:IKXYZ]
Address      : 0x0
Pages        : 256
Page Size    : 4096 bytes
Total Size   : 1024KB
Planes       : 1
Lock Regions : 0
Locked       : none
Security     : false
Erase flash
chipErase(addr=0)
Done in 0.052 seconds
Write 227784 bytes to flash (56 pages)
[                              ] 0% (0/56 pages)write(addr=0x34,size=0x1000)
writeBuffer(scr_addr=0x34, dst_addr=0, size=0x1000)
SAM-BA operation failed

After inspecting the code we were able to narrow this down to the TIMEOUT_QUICK in https://github.com/arduino/BOSSA/blob/nrf/src/Samba.cpp#L660 (more details described in https://github.com/renode/renode/issues/208#issuecomment-834676037). In short - extending timeouts solved the issued and allowed for successful upload of binaries to the virtual device over USB/IP connection.

I was wondering - what is the reason for having both TIMEOUT_NORMAL and TIMEOUT_QUICK and would it be a problem to use TIMEOUT_NORMAL everywhere? This would allow for more reliable communication with virtual devices and USB over IP connections on Linux.

I can prepare a PR with proposed changes, but wanted to discuss the matter first.