Remove forceful "using namespace arduino" from headers

[facchinm]

First step to fix arduino/ArduinoCore-samd#606

[bxparks]

Hi, This is great news. The explicit using statements seem to provide backwards compatibility with existing forward declarations. As noted above, I had to add the using arduino::String statement to make the fix more complete.

I validated your 2 PRs,

• Don't spill arduino namespace in headers ArduinoCore-samd#612
• Remove forceful "using namespace arduino" from headers #144

by switching my git repos to your branches (so basically, I get a samd 1.8.11, plus your changes). I then compiled and uploaded about 70 of my unit tests, across most of my libraries, to an actual MKR1000 that I recently purchased. I had a few hiccups, but eventually got everything working.

There were 3 classes of problems:

1. String forward declarations, fixed by above.
2. More stringent compiler errors and warnings from the SAMD21 compiler. (Every compiler seems to complain about slightly different things...)
3. The breaking change to ::digitalWrite(uint8_t, uint8_t) which is now ::digitalWrite(uint8_t, PinStatus) in the new API.
   • I have to use an explicitly scoped ::digitalWrite() because I have an overloaded digitalWrite() in that class. But ::digitalWrite() does not match your arduino::digitalWrite()) overload. So I had to insert a handful of #if defined(ARDUINO_API_VERSION) statements.

With regards to the 2 PR on my libraries:

• Readd compatibility with samd and megaavr architectures bxparks/AceTime#57
• Reenable support for samd/megaavr bxparks/AceCommon#14

I will check in a version that removes that #error for the SAMD21 core. But I want to retain the blacklist for megaAVR platform until I personally verify that arduino/ArduinoCore-megaavr#62 is fixed on actual hardware. I currently don't have any megaAVR boards, but it's on my shopping list.

I have a question on bxparks/AceTime#57 that you sent: You replaced the #include <Arduino.h> with an #include <arvr/pgmspace.h>. Unfortunately, that breaks the ESP32 platform, where it needs to be #include <pgmspace.h>. I can add some conditional code on ARDUINO_API_VERSION in there, or just keep using #include <Arduino.h> in that .cpp file.

I will update this comment when I have submitted the fixes on my end that adds support for arduino:samd >= 1.8.10.

[bxparks]

I have prepared a series of PRs, which replace the PRs sent to me by @facchinm:

• Readd arduino samd (see #9) bxparks/AceCommon#15
• Readd arduino samd (see #66) bxparks/AUnit#72
• Readd arduino samd (see #45) bxparks/AceTime#58 (depends on the 2 above)

These are designed to reenable arduino:samd when a new version (1.8.12?) is released. The version number of the arduino:samd Core doesn't matter. Instead, I assume that the ARDUINO_API_VERSION number will be incremented for the next release.

I will wait until the new arduino:samd core is pushed out. Then I will re-validate my libraries, and if everything looks right, I will submit my PRs listed above, and everything should be stable again. We can undo the version-pinning of my libraries (arduino/ArduinoCore-samd#607) in the arduino:samd CI workflow if desired.