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BrianP
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Joined: 30/03/2017
Location: Australia
Posts: 292

Posted: 01:06am 22 Nov 2017

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This is probably one for Grogs or Rob - can I still use the console pins on the 'Mite or does the 1455 connection get in the way of this. I suspect I might already know the answer...

If I "have" to use the serial console connection then might I have to remove the 1455 chip, or is there an easier way to enable serial console functionality?

I have an application already developed that really requires the serial console connection for remote control of the E28.

(Would be really nice if either USB or console could have been used at will.)

Thanks

Brian P.

robert.rozee
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Joined: 31/12/2012
Location: New Zealand
Posts: 2462

Posted: 01:46am 22 Nov 2017

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YES, you can do this, but you need to overcome the 1k5 series resistor between TxD on the 1455 and RxD on the MX170. this means that your external serial device needs to be able to sink AND source at least 3mA. the 1k5 series resistors between 1455 and MX170 were specifically included in the design to allow for this sort of application.

see the below schematic:
2017-11-22_104341_E-28_1C_diagram.pdf

cheers,
rob :-)

BrianP
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Joined: 30/03/2017
Location: Australia
Posts: 292

Posted: 01:50am 22 Nov 2017

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Rob - thanks so much - just what I wanted to hear

Brian P.

BrianP
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Joined: 30/03/2017
Location: Australia
Posts: 292

Posted: 02:03am 22 Nov 2017

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One last question (I hope) - I see from the schematic that the 1455 is also connected to the 'Mite pins 4 & 5. If I am using pins 2-7 & 9 for a keypad, does this have any unforeseen ramifications? It seems to work fine.

Ta

Brian P.

robert.rozee
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Joined: 31/12/2012
Location: New Zealand
Posts: 2462

Posted: 02:54am 22 Nov 2017

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when not in programming mode, the 1455 tristates the connection to pins 4 and 5 of the MX170, so should, in theory, have no (or at least negligible) effect on the function of the pins.

cheers,
rob :-)
Edited by robert.rozee 2017-11-23

BrianP
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Joined: 30/03/2017
Location: Australia
Posts: 292

Posted: 03:41am 22 Nov 2017

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Ta muchly

B

Phil23
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Joined: 27/03/2016
Location: Australia
Posts: 1667

Posted: 08:27pm 22 Nov 2017

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robert.rozee said this means that your external serial device needs to be able to sink AND source at least 3mA.

Rob,

Can you answer of the top of your head whether most of the commonly used modules are capable of this?

Thinking ESP-01's etc for WiFi.
as well as HC-05 & HC-06 for Bluetooth,
HC-11 & HC-12 for 433MHz applications.

Thanks

Phil.

robert.rozee
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Joined: 31/12/2012
Location: New Zealand
Posts: 2462

Posted: 11:22pm 22 Nov 2017

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you would have to try each one and see, i suspect that many may have 1k series resistors that would cause a problem. your best bet is to just place a buffer in front of pin 12. for example a 74LVC1G34 (single buffer in an SMD package), or i believe an LM555 can also be wired up as a buffer/driver.

cheers,
rob :-)

Quazee137

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Joined: 07/08/2016
Location: United States
Posts: 600

Posted: 10:49am 23 Nov 2017

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Here is a few other options like Rob's

dual Optocoupler

SN74LVC2G17 Dual Schmitt-Trigger Buffer

SN74LVC2G241

Quazee137Edited by Quazee137 2017-11-24

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