Question re: RTS/CTS flow control

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Constantin

Constantin

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I am looking into using RTS/CTS with a set of Xbee radios on Serial 3. Looking through the UART page, I see that I need to use D14 at attach a CTS for serial3. Paul mentions that the CTS of the Teensy needs to be attached to the RTS of the other serial device. i.e.

The RTS output from Teensy should be connected to the CTS input on the other serial device, similarly to the TX output connecting to the other device's RX input. Do not simply connect same-named signals with serial.
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However, the Xbee seems to break that convention as it's manual states:
Hardware Flow Control (CTS). When the DI buffer is 17 bytes away from being full; by default, the module de-asserts CTS (high) to signal to the host device to stop sending data [refer to D7 (DIO7 Configuration) parameter]. CTS is re-asserted after the DI Buffer has 34 bytes of memory available.
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(see page 10-12 of the manual)

In other words, the datasheet suggests that the CTS pin on the Xbee is an output that should be connected to the CTS input on the Teensy. Am I correct?
 
For anyone following in my footsteps, the RTS/CTS naming convention issue also seems to affect the Nimbelink series of embedded cellular modems that copy the Xbee footprint. That is, Teensy CTS should be connected to Nimbelink CTS and Teensy RTS shoudl be connected to Nimbelink RTS.

FWIW, RTS/CTS seemed to work great with two teensy's using Series 1 XBees.
 
Good to know. On some other processors I have used, the CTS was such that the processor would tell the XBee I am full now and the XBee would still send typically two more characters before it stopped, which were lost.
 
KurtE said:
Good to know. On some other processors I have used, the CTS was such that the processor would tell the XBee I am full now and the XBee would still send typically two more characters before it stopped, which were lost.
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Even this case should work on Teensy, without lost characters.
 
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