I2C Forum - Recent Threads

TCA9509 Output Current Specification

David Escandon — Tue, 21 May 2013 17:13:21 GMT

TI Team,

I'm using the TCA9509 is a mixed voltage I2C bus. I have 3.3V on the B side and 2.5V on the A side. The datasheet specifies a 10uA low level output current. However, the datasheet says the A side has a strong pull down resistor of 200 ohms. For a low voltage output of ~.2V, wouldn't this imply a 1mA low level output current? How do you arrive at 10uA? Can you share the driver structure for both the A and B sides?

-David

TCA9517 - About usage of TCA9517

hideto kanemaru — Mon, 20 May 2013 13:18:05 GMT

My customer wants to make VOL small using TCA9517.

Is TCA9517 usable by the circuit of page2 of the attached file ?

And, is TCA9517 usable by the circuit of page3 of the attached file?

please give me advice.

I think that the circuit of page2 is usable.

=>datasheet P9 “Master devices can be placed on either bus.”

I think that the circuit of page3 is not usable.

=>datasheet P2 “The TCA9517 cannot be connected B side to B side”

By the usage of my customer, the SDA/SCL line has many noises.

(The noise is adverse effects of the cables.)

Therefore,The low level output voltage(VOL) of TAC9517 may become higher than "Low level input voltage(VIL=0.99V)" of the Slave device.

(the circuit of page1 of the attached file)

So my customer intends to prevent the adverse effects of the noise by making VOL small.

・TCA9517 1chip Circuit VOL = 0.6V (attached file page1) => now

・TCA9517 1chip Circuit VOL = 0.2V (attached file page2) => in review 1 (My idea)

・TCA9517 2chip Circuit VOL = 0.2V (attached file page3) => in review 2 (My customer idea)

Regards,

Kanemaru

TCA9539: Max. Leakage Current for VCC=0V and VI=-0.5V...+5.5V

spider49921 — Thu, 23 May 2013 07:54:34 GMT

Would you please specify the max. leakage current for VCC=0V and VI=-0.5V...+5.5V of the TCA9539 (-> power supply voltage switched off) ?

PCA9534A

ROSA GONZALEZ — Wed, 22 May 2013 15:56:26 GMT

Hi all, I am using the ic pca9534A , am not using the INT OUTPUT PIN, no used no connection. Is there any problem if I dont connect the INT PIN?.

Regards and Thanks in advance

Rosa

P82B96 - Interfacing an IC with VIL(MAX)=0.6V

Kawai — Wed, 15 May 2013 17:10:23 GMT

Hi team,

Our customer is using P82B96 but having problem to interface IC with VIL(MAX)=0.6V.

P82B96 VOL(MAX) Sx,Sy is 1.0V.

How can we interface such IC using P82B96 ?

Please give us your advice.

Best Regards,

Kawai

Question about TCA8424 operation

Peter Ladanyi — Thu, 09 May 2013 09:10:46 GMT

Hi,

I am finding a chip for a new design scanning keyboard matrix and the TCA8424 would be a right solution.
But, I have a question about handling the order of simultaneous pressed keys (keyboard buffer/FIFO) which is not answered by datasheet (or I missed it).

How TCA8424 works when several buttons are pressed between two read operation (input report) via I2C?

For example, how would be stored data in input report structure in these cases?

Case-1:
1.1. no pressed buttons, no interrupt request signals (stable system state)
1.2. 'A' button has pressed, then released
1.3. 'B' button has pressed, then released
1.4. ISR has been performed by CPU, and data is read from TCA8424

Case-2:
2.1. no pressed buttons, no interrupt request signals (stable system state)
2.2. 'B' button has pressed, then released
2.3. 'A' button has pressed, then released
2.4. ISR has been performed by CPU, and data is read from TCA8424

Peter

PCA9306 / about operate condition

KENSUKE YAITA — Fri, 17 May 2013 13:07:54 GMT

Hi,

I'd like to ask about PCA9306.

Is it possible to operate under below schematic condition?

My customer designed test jig but mistake to set I2C Bus Master to 3.3V MCU, and use 51kΩ.

This circuit makes no sense as a level shifter, there is no problem if it operate nomally.

But, I think it has a problem because it deviate from specification below.

Could you give me an advice?

Regards,

Yaita

how I2C master receiver acknowledges to slave

Dharani R — Thu, 16 May 2013 09:06:03 GMT

hi,

Can anyone explain how the I2C master receiver acknowledges to slave when it gets one byte of data from slave.

TCA8418 interface to microcontroller

harnek singh — Tue, 14 May 2013 09:53:41 GMT

Hello Dear

I want to interface TCA8418 keypad scan ic with microcontroller.

will any body suggest me the initialization of tca8418 for interfacing , or any sample code to refer .

thanks

PCA9306 VEN&VREF2 > SCL&SDA

Tomohiko Sugiyama — Tue, 07 May 2013 02:03:07 GMT

If VEN&VREF2 is larger than SCL&SDA ,will be problems ?

For example

Vref1&SCL1&SDA1=+1.2V(pull up)

VEN&VREF2=3.3V CMOS (High:3.2V~3.3V,Low:0V~0.1V)

SCL&SDA = +3.3V (pull up)

I'm worried about the state of VEN & VREF2 = 3.2V.

Best regards

can i use iso7241 as an i2c isolator??

Orkun KASAPOGLU — Mon, 29 Apr 2013 07:41:56 GMT

Hi I have a problem with my pcb drawings. I'm using ads7828 but missed out it was i2c interface and i use iso7241 with adc ic. Can I use iso7241 (with short circuit its pin (5-6) and (11-12)) like an i2c sda pin. I have to find answer immediately. Thanks.

PCA9539 - unused I/O ports

Kawai — Tue, 23 Apr 2013 14:20:31 GMT

Hi, could you please tell me what to do with the unused I/O p-ports ?

I believe that they should be pulled down or up to keep logic low or logic high.

Our customer uses this device leaving the unused port open.

If they assign the port as an output, could they leave the port open ?

I am worrying the behavior of the device which the I/Os are configured as input when at power-up.

Thanks and Best Regards,

Kawai

USB to GPIO firmware/software

franck morisseau — Tue, 06 Mar 2012 18:52:21 GMT

Hello.

i've bought an USB to GPIO adapter because i'm searching for I2C adapter.

in the documentation theres a evaluation software where we can send some I2C byte. but where i can find this application? i've got nothing in the box except usb and ribbon adapter. no CD and no original firmware.

thank you for your help.

greetings

Process technology

Nick Cheng — Wed, 17 Apr 2013 10:00:21 GMT

Dear Sir/Madam,

What is the process technology used to fabricate the TCA6416APWR | TCA6424A, is it purely based on bipolar technology, CMOS, BiCMOS? We will like to know the underlying IC technology.

Thanks

I want to use 4 PCA9306 as a 1-to-4 i2c bus expander, to isolate identical slaves with the same chip address.

john bremsteller — Wed, 01 May 2013 00:48:03 GMT

There is no level translation or buffering desired, only a switch function via the EN pin, going 1.8v to 1.8v . The datasheet

does not exclude this functionality, although it dies not directly list it as a use case. The pullups are 1.5k on each side and

the EN signal high is 1.8v. Do you see a problem with using the PCA9306 this way?

TCA6424ARGJR Power Pad

Patrick McNamara — Wed, 24 Apr 2013 12:43:52 GMT

Where can I find specific directions for how to mount the UQFN package... specifically, I am looking for how to hand the Exposed Power Pad. Do I ground? Thanks.

LM75 I2C power sequence

guoxing zhang — Wed, 24 Apr 2013 07:06:41 GMT

Hi,

I our case, the power rail(VCC_3V3_A) of LM75 and the pull up resistors power rail(VCC_3V3_B) are different. See the circuit below.

the pull up resistors we are using is 1KOhm.

My question is if the VCC_3V3_A power up later than VCC_3V3_B, is there any risk? Like latch up or back driving?

Thanks

Guoxing

TCA9517 vcca and vccb

wayne halcomb — Mon, 22 Apr 2013 16:21:46 GMT

I have an app that uses the standard interface is shown

but my A-side a a side that I have a device under test. During that test VCCA needs to change from 1.5V to 3.6V.

Can VCCA be higher than VCCB and still work?

If not is there aanother product I can use?

Thanks

McBsp

allen k — Fri, 19 Apr 2013 02:07:20 GMT

I am a poststudent from China.How can I use the TMS320c64'McBsp to communicate with four sensor.The sensor's port is I2C.Thanks.

Process technology

Nick Cheng — Wed, 17 Apr 2013 10:19:36 GMT

Dear Sir/Madam,

What is the process technology used to fabricate the TCA9539PWR, is it purely based on bipolar technology, CMOS, BiCMOS? We will like to know the underlying IC technology.

Thanks

PCA9517 SCL and SDA swapped due to pinout mistake - will it still work?

ed kornegay — Wed, 17 Apr 2013 16:14:34 GMT

PCA9517: I2C Level-translating Bus Repeater. We are using it for SMBus.

The component on the A side of the chip had a mistake in the SMBus pinout, so on my board SCL is wired to pin 3 (SDAA) and SDA is wired to pin 2 (SCLA).

The B side is wired correctly.

It is much easier and more reliable to swap the lines on the B side of the chip. This means that SCL would be traveling through the buffers meant for SDA, and SDA through the SCL buffers.

The chip datasheet shows two bidirectional buffers with no control logic. But we are worried that the chip is not as simple as that, and that there is logic that will cause errors when we use it backwards.

What do the experts think?

TIA

Ed K

P82B96 on flat cable

Mahendrakumar Reddy Ippagunta — Fri, 12 Apr 2013 14:56:09 GMT

We are using P82B96 with one master and one slave connected with 3 mtr cable. The datasheets and app notes recommend two twisted pairs. Can we use 4 wire flat cable (no twisted pairs)? Do you have any tests conducted with flat cable for this length? VCC of P82B96 is 5V and I2C logic level is 3.3V.

-Mahendra

Problem with I2C on MSP430F5529

Sachin Nayak — Wed, 10 Apr 2013 19:01:37 GMT

We need to communicate between MSP430F5529 and BQ24272 using I2C. I wrote functions to do I2C with MSP430F5529 as master and it worked well with Arduino. This is the code:

#include <msp430.h>
#include "Clock.h"
#include "uart.h"
//#include "I2C.c"

unsigned char TXData;
unsigned char RXData;

void I2C_init(unsigned char SA)
{
UCB1CTL1 |= UCSWRST; // Enable Software reset so that I2C can be configured
UCB1CTL0 = UCMST + UCMODE_3 + UCSYNC; // I2C as Master, synchronous mode
UCB1CTL1 = UCSSEL_2 + UCSWRST; // Use SMCLK, keep SW reset so that Baud rate can be set
UCB1BR0 = 62; // fSCL = SMCLK/UCB1BR
UCB1BR1 = 0;
UCB1I2CSA = SA; // Sets slave address
UCB1CTL1 &= ~UCSWRST; // Clear Software Reset so that I2C can continue
UCB1IE |= UCTXIE; // Enable TX interrupt
UCB1IE |= UCRXIE; // Enable RX interrupt
}

void I2C_send(unsigned char Data)
{
TXData = Data; // Holds TXData
UCB1CTL1 |= UCTR + UCTXSTT; // Set transmitter mode, generate start condition
}

void I2C_receive()
{
UCB1CTL1 &= ~UCTR; // Sets receiver mode
UCB1CTL1 |= UCTXSTT; // Generate start condition
}

int main(void)
{

WDTCTL = WDTPW + WDTHOLD; // Stop WDT

initCLK(); // Set clock to 25 MHz

P4SEL |= 0x06; // Assign I2C pins to USCI_B0

P4DIR ^= BIT4; // Check whether code is running by lighting an LED
P4OUT |= BIT4;
int i,j;
//for (i =20000;i>0;i--);
P4OUT &=~BIT4;

_bis_SR_register(GIE); // Enable interrupts

I2C_init(0x6B);

I2C_send(0x01);

I2C_receive();
uart_init();
UART_send_char(RXData);
}

//------------------------------------------------------------------------------
// The USCIAB0_ISR is structured such that it can be used to transmit any
// number of bytes by pre-loading TXByteCtr with the byte count.
//------------------------------------------------------------------------------
#pragma vector = USCI_B1_VECTOR
__interrupt void USCI_B1_ISR(void)
{
switch(__even_in_range(UCB1IV,12))
{
case 0: break; // Vector 0: No interrupts
case 2: break; // Vector 2: ALIFG
case 4: break; // Vector 4: NACKIFG
case 6: break; // Vector 6: STTIFG
case 8: break; // Vector 8: STPIFG
case 10:
RXData = UCB1RXBUF; // Reads data
UCB1IFG &= ~UCRXIFG; // Clears interrupt flag
break; // Vector 10: RXIFG

case 12: // Vector 12: TXIFG
// while (!(UCB1IFG & UCTXIFG)); // Checks whether start condition is generated
UCB1TXBUF = TXData; // First data to be transmitted can be written

while (UCB1CTL1 & UCTXSTT); // If slave acknowledges the address, the UCTXSTT is cleared

while (!(UCB1IFG & UCTXIFG)); // Checks whether data is put into the shift register from the buffer
UCB1CTL1 |= UCTXSTP; // Completes the transmission
UCB1IFG &= ~UCTXIFG; // Clears interrupt flag
break;
default: break;
}
}

But when I try to send the address of the register to be read from the BQ24272 through I2C, the code gets stuck in the line, "while (!(UCB1IFG & UCTXIFG)); // Checks whether data is put into the shift register from the buffer ", even though the execution of the previous line means that the slave has acknowledged the address.

High Icc current seen on unused inputs in a recent lot of TCA9539 Port expanders

Skip Tobey — Thu, 04 Apr 2013 13:32:40 GMT

We have been using the TCA9539 in our battery operated product for about 2 years without issue.

Recently we noticed a very high battery current demand of about 2mA instead of our typical 26uA demand.

We traced this to TCA9539 devices with a top print code of PW539 29K G4 ASSD. Replacing this with a device marked OAK G4 A89H resolves the issue.

The problem seems to be with I/O ports that are not connected (floating) and set as inputs on the PW539 29K G4 ASSD devices. In the same circut, the devices marked OAK G4 A89H and all previous devices do not exibit this problem.

My questions are:

1. Has there been any changes or production issues in the TCA9539 PW539 29K G4 ASSD that may have created this issue for us.

2. Would setting the unconnected I/O pins to low driven outputs rather than inputs resolve this issue.

Thanks,

Skip Tobey

PCA9306 for a battery powered application?

Nicola 76855 — Mon, 08 Apr 2013 08:02:42 GMT

Hi,

I am planning to use the PCA9306 in a battery powered application. In this case the VREF1 will change between 2.7V and 3.6V depending the battery level. On VREF2 I will have a 3.3V generated by DC/DC converter that I can not use for I2C master device.

Is this a problem? It seems that VREF1 has to be always less than VREF2, is this right?

Do you have some advice or different components for this kind of application?

Thank you in advance,

Nicola