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  • malexead commented on silver_a's instructable Inspector Roomba1 year ago
    Inspector Roomba

    a. It's definitely worth testing your modules with a USB-TTL dongle first, with AT commands and a serial terminal of some sort, to see what speeds work on the module, and to set it to whatever your Roomba uses. My Roomba 400 uses 57.6K, newer ones 115.2K. My HC-05 and -06 modules work fine with both those speeds. YMMV.b. Most bluetooth modules, while they allow power in @ 5v (converted to 3.3 v. by onboard VR), actually use I/O TTL @ 3.3v. [To see which logic level your module uses, apply power and measure what's on the Tx and Rx pins, disconnected from other devices.] So while you can get away with connection (as here) to 5v logic that Roomba uses, and it will work for a while, it's reported to destroy the BT module sooner or later. Voltage divider with a couple of resistors is advised...

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    a. It's definitely worth testing your modules with a USB-TTL dongle first, with AT commands and a serial terminal of some sort, to see what speeds work on the module, and to set it to whatever your Roomba uses. My Roomba 400 uses 57.6K, newer ones 115.2K. My HC-05 and -06 modules work fine with both those speeds. YMMV.b. Most bluetooth modules, while they allow power in @ 5v (converted to 3.3 v. by onboard VR), actually use I/O TTL @ 3.3v. [To see which logic level your module uses, apply power and measure what's on the Tx and Rx pins, disconnected from other devices.] So while you can get away with connection (as here) to 5v logic that Roomba uses, and it will work for a while, it's reported to destroy the BT module sooner or later. Voltage divider with a couple of resistors is advised for the Roomba output (Tx) to HC-05,6 input (Rx). No need to modify the module Tx to Roomba Rx wiring -- 3.3v looks HIGH to the Roomba.

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