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Modify UART Class to Make Use of the txBuffer #304

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c180836
Use txBuffer
delta-G May 6, 2024
b4a4e37
fixed formatting
delta-G May 6, 2024
e975966
added availableForWrite
delta-G May 6, 2024
2878c5a
Use member variable in ISR instead of static veriable
delta-G Jun 29, 2024
0a14d85
Loads characters 16 at a time in the interrupt callback
delta-G Jul 3, 2024
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fixed formatting
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@delta-G
delta-G committed Jun 30, 2024
commit b4a4e37c59f2d3ceff941a654992e3135dacd9e8
56 changes: 28 additions & 28 deletions cores/arduino/Serial.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -61,13 +61,13 @@ void UART::WrapperCallback(uart_callback_args_t *p_args) {
case UART_EVENT_TX_COMPLETE:
case UART_EVENT_TX_DATA_EMPTY:
{
if(uart_ptr->txBuffer.available()){
static char txc;
txc = uart_ptr->txBuffer.read_char();
R_SCI_UART_Write(&(uart_ptr->uart_ctrl), (uint8_t*)&txc , 1);
} else {
uart_ptr->tx_done = true;
}
if(uart_ptr->txBuffer.available()){
static char txc;
txc = uart_ptr->txBuffer.read_char();
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@angavrilov angavrilov Jun 26, 2024

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Is it OK to use a static variable here instead of uart_ptr->txc? Would this work correctly if there are multiple uarts working simultaneously?
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@delta-G delta-G Jun 27, 2024

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That's a good question. I made it static because it was being passed as a pointer on the next line but I didn't really think about it being there in multiple instances.

I think that it will be OK because R_SCI_UART_Write is going to use that data one line later and then we're done with it. I think it would be OK to make it not static.

I wish I could grab a whole chunk of the tx_buffer there so the code in r_sci_uart.c could make effective use of the FIFO. The problem is that I would need to know where the data in the tx_buffer wraps around or I could run off the end.

I have a separate branch that uses DMA and it doesn't have this problem because I set the DMA extended repeat area to match the tx_buffer and the DMA controller will automatically wrap back around. But that code seems to be broken in other places.
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@delta-G delta-G Jun 27, 2024

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Actually, looking at it now, I don't see why I don't just use uart_ptr->txc instead. Maybe I thought because it was an interrupt handler that I wouldn't have access but I do.

I'll update the branch tonight and retest a little.
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@delta-G delta-G Jun 29, 2024

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I updated the code to use the member variable instead. It tests ok. I did a lot of printing without any failures. Unfortunately I seem to have messed up my branch.
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@delta-G delta-G Jul 3, 2024

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Updated once more to load characters 16 at a time in the interrupt callback. This takes advantage of the FIFO to reduce the number of interrupts.
R_SCI_UART_Write(&(uart_ptr->uart_ctrl), (uint8_t*)&txc , 1);
} else {
uart_ptr->tx_done = true;
}
break;
}
case UART_EVENT_RX_CHAR:
Expand Down Expand Up @@ -112,31 +112,31 @@ bool UART::setUpUartIrqs(uart_cfg_t &cfg) {
/* -------------------------------------------------------------------------- */
size_t UART::write(uint8_t c) {
/* -------------------------------------------------------------------------- */
if(init_ok) {
while(txBuffer.isFull()){;}
txBuffer.store_char(c);
if(tx_done){
tx_done = false;
txc = txBuffer.read_char(); // clear out the char we just added and send it to start transmission.
R_SCI_UART_Write(&uart_ctrl, (uint8_t*)&txc , 1);
}
return 1;
}
else {
return 0;
}
if(init_ok) {
while(txBuffer.isFull()){;}
txBuffer.store_char(c);
if(tx_done){
tx_done = false;
txc = txBuffer.read_char(); // clear out the char we just added and send it to start transmission.
R_SCI_UART_Write(&uart_ctrl, (uint8_t*)&txc , 1);
}
return 1;
}
else {
return 0;
}
}

size_t UART::write(uint8_t* c, size_t len) {
if(init_ok) {
for(int i = 0; i<len; i++){
if(init_ok) {
for(int i = 0; i<len; i++){
write(c[i]);
}
return len;
}
else {
return 0;
}
}
return len;
}
else {
return 0;
}
}

/* -------------------------------------------------------------------------- */
Expand Down