I am working on a product (called MDU) with the classic IrDA interface. A TI decoder TIR1000 lies between the MCU and the Irda transceiver.
The workflow is basically like this: MDU's MCU sends a byte with baudrate 9600 to TIR1000 through UART. This signal is then transformed and sent to MDU's transceiver, then to a terminal's transceiver and at last to the terminal's MCU. After that, the terminal answers with the same byte and sends it back.
( MCU <-> TIR1000 <-> Transceiver) <-> (Transceiver <-> MCU)
( MDU ) ( Terminal )
Signal "MDU Tx" is the signal on UART, namely TIR1000's Input.
Signal "MDU Transceiver Tx" is TIR1000's output to MDU's Transceiver.
Signals "Term. Rx" and "Term. Tx" are on the terminal side.
As you can see, once the terminal receives this byte, it will reponse. Important, the time between cursor A and B is exactly 520us (= 104us * 5) after TIR1000's conversion. This is also the ideal time for continuous four 0's in one byte.
In the second picture the MDU's MCU sends out the same byte in the same baud rate. The time for the four 0's on UART is still ideal, however, after TIR1000's conversion, the time between cursor A and B is no more 520us as the first example, but approximately 515us. As a result, the terminal receives a non-standard IrDA signal and does not response.
The hardware design has been checked. The crystal oscillator provides a correct and stable frequency to TIR1000.
This problem bothers me a lot. Any help is appreciated.
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