I start draw new schematic and PCB for GL-865 DUAL module.
I want use only Rx and Tx pin (no hardware flow controll )
other pin (DTR,RTS) can be leftopen or need any pin connect to pull-up or to GND???
on Note (GL-865 hardware guide) is write
NOTE:The UART input line TXD (rx_uart) of the GL865 is NOT internally pulled up with a resistor, so there may be the need to place an external 47KΩ pull-up resistor, either the DTR (dtr_uart) and RTS (rts_uart) input lines are not pulled up internally, so an external pull-up resistor of 47KΩ may be required.
There is more at page 14 of Hardware User Guide, I would say that you should provide the pull-up resistors.
I read this manual.
it’s mean so if don’t want hardware flow control then put RTS pin to GND ,
and DTR can put too to GND or use pull-up resistor to 2.8V or no matter how or in what state is??
receive data in GSM module is max 2.8V , for this I wan use NC7SZ08 TinyLogic AND Gate. this gate power from PWRMON pin on GSM module (Vout is 2.8V).
If GSM module is OFF then PWRMON is 0V and input and output NC7SZ08 are in high impedance state. this solution I want use for : back powering effect it is recommended to avoid having any HIGH logic level signal applied to the digital pins of the GL865 when the module is powered OFF or during an ON/OFF transition.
Indeed I think to avoid back powering effect RTS and DTR should be also tied to ground; of course the signal level is irrelevant from flow control point of view if is not used. However you are aware of what problems can appear (data lost) if you don’t use flow control during data transfer, for example in case of network problems right?
And I know you are looking for a method to quickly interrupt a connection and go in command mode, DTR can be useful, see AT&D command.
More, DTR is used for power saving purposes, so is quite an essential pin.
back powering only for TX pin in GSM module , RTS in my all project is on GND.For DTR , is good , but I test +++ and work good too, don’t need hardware control (free one pin), PS: if I have GL-865 what firmware is on it??? wersion xx.xx.3 or 4
If you have it, AT+CGMR will say. If is a future purchase, is a matter of when and where the purchase.
but I PCB draw now , i don’t have it soldered and I can’t test any AT command.
what first firmware are burn to gl-865??if you don’t know , OK . if create first prototype then test it.
As .x4 is not yet out, I suppose is .x3. Put pads on RX/TX to upgrade!
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