Improvements in STM32 I2C class lib code

[josesimoes]

Description

• Remove static write and read buffers for I2C
• Add function to compute estimated time to perform I2C transaction
• Rework I2C NativeTransmit to use CLR events (or not) depending on transaction time
• Remove I2C init and uninit calls (not required anymore)
• Remove target configurations for I2C (not required anymore)

Motivation and Context

• Resolves I2C does not send correct data Home#319

How Has This Been Tested?

All tests reading and writing from/to STMPE811 touch controller in STM32F429I-DISCO.
The writings were performed to setup the touchscreen controller operation which was returning coordinates as expected.

Reading ChipID inside loop (straight through operation, no CLR thread swap)

            byte[] buffer = new byte[2];
            Windows.Devices.I2c.I2cTransferResult readResult;

            for (; ; )
            {
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
            }

Time between transactions: 0.228[ms]

Reading 220 bytes from chip inside loop (exceeds thread execution quantum, continuation setup, returning transaction result on following execution)

            byte[] buffer = new byte[220];
            Windows.Devices.I2c.I2cTransferResult readResult;

            for (; ; )
            {
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
            }

Time to setup read address and read 220 bytes : ~18[ms]
Time between transactions: 10.81[ms]

Reading ChipID on 10 consecutive transactions (straight through operation, no CLR thread swap)

            byte[] buffer = new byte[2];
            Windows.Devices.I2c.I2cTransferResult readResult;

            for (; ; )
            {
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
                readResult = _touchController.WriteReadPartial(new byte[] { 0 }, buffer);
            }

Time to setup read address and read 2 bytes : ~0.47[ms]
Time between transactions: 0.1924[ms]

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Signed-off-by: josesimoes jose.simoes@eclo.solutions

[nfbot]

Hi @josesimoes,

I'm nanoFramework bot.
Thank you for your contribution!

A human will be reviewing it shortly. 😉

[ghost]

There must be something wrong as nothing has changed on my side :(
I still have the 10ms penalty and the duplicate data when I read :

[josesimoes]

You seem to have the correct version.

That timing you see there between transactions is because of that Thread.Sleep()
When you call that, the current thread immediately stops execution and reschedule.
All other threads in the queue - and eligible to run - will get their execution share and the engine gets back to this one which, in the mean time, has become eligible again.

For such short timing I would recommend either do nothing or do a couple of dummy operations just to respect those 5ms that I guess are required for the write operation to complete.
Anyway you can check with logical analyser if the correct timing is happening.

[piwi1263]

LGTM