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Workaround (for reference): Avoid race lock up in usart #45

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Workaround (for reference): Avoid race lock up in usart #45

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5 changes: 5 additions & 0 deletions libmaple/usart.c
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Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,11 @@ void usart_init(usart_dev *dev) {
rb_init(dev->rb, USART_RX_BUF_SIZE, dev->rx_buf);
rcc_clk_enable(dev->clk_id);
nvic_irq_enable(dev->irq_num);

/* Set to max priority to avoid race condition where register presumably
* might change before it can be picked out by USART interrupt and cause
* it to lock up. */
nvic_irq_set_priority (dev->irq_num, 0);
}

/**
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4 changes: 3 additions & 1 deletion libmaple/usart.h
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Expand Up @@ -309,7 +309,9 @@ static inline void usart_putstr(usart_dev *dev, const char* str) {
* @see usart_data_available()
*/
static inline uint8 usart_getc(usart_dev *dev) {
return rb_remove(dev->rb);
/* Use rb_safe_remove to avoid race in case another interrupt have reset
* or cleared the ringbuffer */
return rb_safe_remove (dev->rb);
}

/**
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