Can CP2102 USB to UART be used to power 5V devices?

[ssc953]

I am using CP2102 based USB to UART converter board to interface my UART based radio modem with my PC.
The radio modem works on 5V. I have made the following connections:
Radio Vcc => Converter 5V pin
Radio GND => Converter GND
Radio Tx => Converter Rx
Radio Rx => Converter Tx
However, I am not able to establish communication. I have successfully installed the USB drivers. The CPU activity LED of the radio modem is also not blinking.
Is it because CP2102 cannot drive 5V devices?
or is something else wrong?

 

[(*steve*)]

1) What powers the converter board and how much current can it supply?

2) what current is consumed by the converter board?

3) what excess current can be supplied? (the difference of the above)

4) how much current does the radio modern require?

5) is the current required (5) less than or equal to that available (4)?

 

[ssc953]

1) The converter board is powered by the USB port of the PC. It can supply 500mA.

2) Max current through Vcc and GND = 500mA
Supply Current = 26mA

3) Around 475mA

4) Max current requirement of radio modem: 130mA

5) Yes

Current requirement seems to be fulfilled. Then why isn't the radio modem working?

 

[Kiwi]

A USB2 port can only supply 500mA.

I use a CP2102 board to program and test run Arduino Pro Mini boards and stand alone ATMEGA328P micros without any problems. Just have to limit the output current to keep it well below 500mA.

Must learn to type faster.

 

[ssc953]

Thanks @Kiwi Did you power the Arduino with CP2102 board?
i got confused after reading CP2102 datasheet. It shows 5V pin as power input pin. Can an input pin drive an external device?

 

[Kiwi]

Yes, the CP2102 board was powering the Arduino.
Here is a photo of the programming board I use.

 

[ssc953]

Thanks @Kiwi . Surely then power is not the problem.
Any idea what could be going wrong in my circuit. Why the radio modem does not turn on?
(I know that it will not turn on if Tx and Rx are not properly connected. I have tried switching them)

 

[(*steve*)]

Are you using any of the same pins used by the programmer?

 

[ssc953]

@(*steve*)
I mentioned the connections I'm using in #1. Are you asking something else?

 

[(*steve*)]

Sorry, somewhere along the way I inserted a microcontroller in there somewhere.

What speed is the uart set to and what does the module expect?

 

[ssc953]

USB to UART converter is set at 9600 8N1 according to device manager of PC.
The radio modem has default configuration 9600 8N1

 

[(*steve*)]

Is the device you're trying to talk to an ESP-12 board (aka ESP8266)?

 

[ssc953]

The radio modem I am using is Dorji DRF1276DM.

 

[(*steve*)]

The radio modem I am using is Dorji DRF1276DM.

Well, at least it's not harmed by 5V

Did you note this paragraph in the datasheet:

If the EN pin of the node is connected to logic high, the node module will enter into sleep mode. If the EN pin is connected to logic low, the node module will work in one of the two communication ways (normal speed communication and breath period communication) according to the logic level of SET pin. If the SET pin is set to high, the node module will keeps CAD wireless monitor to detect if there is any wireless signal coming at the interval of the breath period. If the SET pin is set to logic low, the node module will keep in receive mode so the central module will not need to send long preamble. That's why the logic level of SET for central module must be the same as the node module.

Given that the pins are noted as having TTL inputs, it is entirely possible leaving an input open will cause it to float high. In any case, I don't see it's speced to have this pin left open.