Improve CDC read code #1953
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Improve CDC read code #1953
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Read CDC data from USB FIFO on demand instead of in ISR. Remove superfluous ring buffer. Signed-off-by: Paul Brook <paul@nowt.org>
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It seems like your modified peek function should be |
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You are right. Patch fixed and branch updated. |
| ring_buffer *buffer = &cdc_rx_buffer; | ||
| return (unsigned int)(SERIAL_BUFFER_SIZE + buffer->head - buffer->tail) % SERIAL_BUFFER_SIZE; | ||
| if (peek_buffer >= 0) { | ||
| return 1; |
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I guess that the
return 1;
should be:
return 1 + USB_Available(CDC_RX);
To avoid situations where queued chars may seems to "disappear":
av1 = Serial.available(); // av1 may be > 1
Serial.peek();
av2 = Serial.available(); // after the peek av2 is 1
assert(av2>=av1); // Assertion fails if av1>1
cmaglie
added a commit
that referenced
this pull request
May 30, 2014
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This PR introduced a regression. I've opened issue #2123 |
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Remove superfluous ring buffer from the CDC read code. The USB hardware already buffers 128 bytes of data, so just read from that on demand.
The result is smaller, faster, uses substantially less ram, and does not do large data copies in an interrupt handler.