K64F: Add support for SERIAL ASYNCH API

[mmahadevan108]

Description

K64F: Add support for SERIAL ASYNCH API

Status

**READY

• Tests
  Tested both DMA and interrupt implementation using test code from below link:
  https://developer.mbed.org/teams/SiliconLabs/code/Serial-LowPower-Demo/file/7136baf24c9c/main.cpp

[mmahadevan108]

@maclobdell @0xc0170 @bridadan

[sg-]

@AlessandroA Review of DMA usage?

/morph test

[mbed-bot]

Result: SUCCESS

Your command has finished executing! Here's what you wrote!

/morph test

Output

mbed Build Number: 1272

All builds and test passed!

[AlessandroA]

@sg- @0xc0170 @meriac From the uVisor point of view our expectation is that all uVisor K64F tests should fail because of this PR, as they all use the serial port via printf.

Since all uVisor tests pass we guess that the async/DMA'd version of the APIs is not actually used by default. If that's the case, it would be useful for us to see an example snippet that uses Serial or RawSerial with DMA. We would turn that snippet into a uVisor test: For the security model, it's important to see that test fail because of this PR.

Once these assumptions are confirmed, we will create a fix to uVisor (similar to this previous one) that allows DMA to work when uVisor is enabled.

[0xc0170]

Since all uVisor tests pass we guess that the async/DMA'd version of the APIs is not actually used by default. If that's the case, it would be useful for us to see an example snippet that uses Serial or RawSerial with DMA. We would turn that snippet into a uVisor test: For the security model, it's important to see that test fail because of this PR.

This is for async methods that are not used for stdout/in, therefore we need an example snippet so you can test it.
@mmahadevan108 Can you provide here the code snippet ? That redirects stdout to own Serial instance and uses async methods to send data ?

[mmahadevan108]

Tested both DMA and interrupt implementation using test code from below link:
https://developer.mbed.org/teams/SiliconLabs/code/Serial-LowPower-Demo/file/7136baf24c9c/main.cpp

The code in the above link uses interrupts. To test DMA, I added the below 2 lines before calling read() in the main function.

---

test_connection.set_dma_usage_rx(DMA_USAGE_ALWAYS);
test_connection.set_dma_usage_tx(DMA_USAGE_ALWAYS);

---

[0xc0170]

@mmahadevan108 We merged the renaming that causing now conflicts?

[mmahadevan108]

I have updated the branch to resolve merge conflicts

[bridadan]

/morph test

[mbed-bot]

Result: SUCCESS

Your command has finished executing! Here's what you wrote!

/morph test

Output

mbed Build Number: 1330

All builds and test passed!

[mmahadevan108]

Anything more needed for this PR?

[bridadan]

@AlessandroA I wasn't sure of your stance on this PR based on your previous comment, could you please review?

[meriac]

@bridadan Please merge the DMA pull request if it works for you - we will fix resulting uVisor (test) breakage. @AlessandroA