UART with CP2103 voltage

[ErikY]

So I bought the CP2103 from spark fun and I am now reading the data sheet.

I am pretty new to data sheets, so I want to make sure I am interpreting this correctly before I fry something.

The board itself clearly shows 3.3v for the vcc, and the data sheet shows a max of 3.6v, however, the data sheet states that the 2103 has an internal 5 to 3V regulator.

Here is the data sheet if anyone is interested:

http://www.sparkfun.com/datasheets/IC/CP2103.pdf

Would that mean it is safe for me to use my regulated 5V from my $50 board?

Originally, I was thinking I may need to make a whole new 3.3V regulated power supply, but based on the above mentioned regulator, I am thinking I am safe.

Can anyone validate my thinking for me?

[Soeren]

Would that mean it is safe for me to use my regulated 5V from my $50 board?

You're not being clear about whether you just got the chip or the breakout board, but I'll assume the latter.

Measure if there's a direct connection between USB connector pin 1 (V+) and CP2103 pin 7 (p8 in the datasheet shows how the pin numbers are arranged). Use an (Ohm-meter.
If there's connectivity, it's driven by the USB power (anything else would be illogical or at least made as options, but do measure anyway).

[ErikY]

Soren,

Thanks for the reply.

I got the breakout board:  http://www.sparkfun.com/products/199

In Admin's tutorial he is showing the vcc and the ground connecting to the $50 robot board's power, so I assumed I needed to do the same thing.

So if there is say at least a 10k resistance between pin 1 and pin 7, are you saying I don't even need to connect the vcc and the gnd to my augmented micro controller at all, only the tx and the rx?

Thx!

[Soeren]

Hi,

So if there is say at least a 10k resistance between pin 1 and pin 7,

NO!
If there's very little resitance, say a few Ohm tops (to account for contact error and such - it will be a copper trace if it's there)

are you saying I don't even need to connect the vcc and the gnd to my augmented micro controller at all, only the tx and the rx?

You always need to connect the ground.

[ErikY]

Hi,

So if there is say at least a 10k resistance between pin 1 and pin 7,

NO!
If there's very little resitance, say a few Ohm tops (to account for contact error and such - it will be a copper trace if it's there)

are you saying I don't even need to connect the vcc and the gnd to my augmented micro controller at all, only the tx and the rx?

You always need to connect the ground.

Gotcha, I misread your original post, makes sense.

Just out of curiosity, if they are connected, and it is powered by the USB, what would the vcc be used for, in what scenario?

[Soeren]

Hi,

The CP2103 includes an on-chip 5 to 3 V voltage regulator. This allows the CP2103 to be configured as either a
USB bus-powered device or a USB self-powered device. These configurations are shown in Figure 7 and Figure 8.
When enabled, the 3 V voltage regulator output appears on the VDD pin and can be used to power external 3 V devices. See Table 9 for the voltage regulator electrical characteristics.

[ErikY]

Hi,

The CP2103 includes an on-chip 5 to 3 V voltage regulator. This allows the CP2103 to be configured as either a
USB bus-powered device or a USB self-powered device. These configurations are shown in Figure 7 and Figure 8.
When enabled, the 3 V voltage regulator output appears on the VDD pin and can be used to power external 3 V devices. See Table 9 for the voltage regulator electrical characteristics.

Soren, thanks again for your help, I know I am somewhat dense with this stuff as it is pretty new to me.

So, this makes sense to me, I have been working off of Admin's tutorials, and in this pic:

http://www.societyofrobots.com/images/microcontroller_uart_50_connect.JPG

He is clearly connecting vcc to the $50 robot micro controller regulated 5v.

I am assuming that is because the serial port ? is not self powered like a USB?

And this would mean I can connect my Rx, Tx to my PD0, PD1 respectively, and connect ground to any ground prong available on my sensor/servo bus and I should be good, leaving out the vcc completely, all of course assuming pin 1 and pin 7 are in fact connected?

[Soeren]

Hi,

He is clearly connecting vcc to the $50 robot micro controller regulated 5v.

I am assuming that is because the serial port ? is not self powered like a USB?

Yes. The serial port haven't got a power rail like USB

And this would mean I can connect my Rx, Tx to my PD0, PD1 respectively, and connect ground to any ground prong available on my sensor/servo bus and I should be good, leaving out the vcc completely, all of course assuming pin 1 and pin 7 are in fact connected?

Yes, but connect the ground solidly, either to the nearest ground, or to close to the bttery ground terminal - no wildly flying wires.

You may need level converters between the board and the microcontroller - check the I/O levels (as spec'd in the datasheet for your microcontroller).

[ErikY]

Hi,

He is clearly connecting vcc to the $50 robot micro controller regulated 5v.

I am assuming that is because the serial port ? is not self powered like a USB?

Yes. The serial port haven't got a power rail like USB

And this would mean I can connect my Rx, Tx to my PD0, PD1 respectively, and connect ground to any ground prong available on my sensor/servo bus and I should be good, leaving out the vcc completely, all of course assuming pin 1 and pin 7 are in fact connected?

Yes, but connect the ground solidly, either to the nearest ground, or to close to the bttery ground terminal - no wildly flying wires.

You may need level converters between the board and the microcontroller - check the I/O levels (as spec'd in the datasheet for your microcontroller).

So my plan was to use a molex connector to connect the ground to my micro controller board, I will connect it to the closest available pin, which would come right after my sensors.

When you say level converters, I am completely lost, do you mean voltage level converters?

Thx again!