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micropython / micropython-esp32

Old port of MicroPython to the ESP32 -- new port is at https://github.com/micropython/micropython
MIT License
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UART.write loses 2 bytes #114

Closed rdagger closed 7 years ago

rdagger commented 7 years ago

After I initialize UART2, the first 2 bytes written disappear. After the 2 lost bytes, it works as expected. For example with the following code only the last 2 bytes 0x03 and 0x04 are transmitted:

from machine import UART
uart = UART(2, 9600)
uart.write(bytes([0x01, 0x02, 0x03, 0x04]))

Issuing the write statement a 2nd time transmits all 4 bytes.

dpgeorge commented 7 years ago

Yes, I saw this bug as well. I think it's a bug in the Espressif IDF and I posted an issue about it: https://github.com/espressif/esp-idf/issues/710

In the meantime, if you really need to have it fixed, you can disable the TX buffer in the UART by changing the uart_driver_install line to (tho 32 becomes a 0):

uart_driver_install(uart_num, 256, 0, 10, &UART_QUEUE[self->uart_num], 0);
rdagger commented 7 years ago

Thanks, only the first write statement is affected. My work-around is to call uart.write(bytes([0x00])) after the init statement. Subsequent write statements work correctly.

dpgeorge commented 7 years ago

This is fixed in 965027d7c9595cdc265f3b5110e78b2a50312178, where the TX buffer is increased to 64 bytes.