> So, anything that happens in the usart interrupt handler is transparent to the codec encoder
Except for timing. But Brady has already explained that it's timing-insensitive. On Tue, Sep 6, 2016 at 3:56 PM, glen english <g...@cortexrf.com.au> wrote: > Eric. you said : "you can not implement a software FIFO on interrupt > because this would effect the other processes every time a byte is > received." > > That is not really the case .I'll explain. > > the interrupt handler will push the used registers, SP etc onto the > stack on entry to the IRQ handler, and restore them when it is done. > So, anything that happens in the usart interrupt handler is > transparent to the codec encoder- it wont ever know there was an > interrupt. The compiler will deal with all that for you. Yes I know in > asm days, life was different. > > but I guess you already know the above.. maybe the case of cycles > > There are plenty of online examples. > > Essentially on stm32 > > on IRQ entry > > read USART->SR into a variable > if there are errors , read the DR. > this will clear errors. it will also get a char if there was one there. > > if there were no errors , but the RXNE / fifo flag was set, and you have > not read the DR already, read the DR and put your new char into your ram > buffer, increment the buffer ptr index, wrap as required and increment > the nChars variable so your app knows how many chars there are > > if the TXE flag was set, the usart wants another char, get from your ram > buffer and write to the DR, inc buffer ptr, and -- nChars to tx. > > done. > > now, in your application, you need sample the nchars waiting to tx, and > n chars ready to get from the buffer variables, and because the irq > context also has access to those registers, you need to guard > application access (ie non irq context) by using critial sections . in > the simplist form that is disabling and enablign interrupts around those > variables > > NOW !!!!! > > there are some very handy synchronization opcodes you can use in the ARM > instruction set to do this!!! > if you want- no need for critical sections and disabling interrupts. > > g > > > > > ------------------------------------------------------------ > ------------------ > _______________________________________________ > Freetel-codec2 mailing list > Freetel-codec2@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >
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