8-bit MicrocontrollersのトピックRe: Configuration problem by using 13192SARD boards and the SHT11 humidity

Configuration problem by using 13192SARD boards and the SHT11 humidity

psy — Mon, 17 Dec 2007 12:51:06 GMT

I have to built up a wireless sensor network by using the 13192SARD boards and the SHT11 humidity sensors.I have a problem in the configuration of the I/O ports of this board and the sensor pins.May anyone experience about it and tell me about the solution ?Thanks in advance....

Re: Configuration problem by using 13192SARD boards and the SHT11 humidity

bigmac — Tue, 18 Dec 2007 01:19:42 GMT

Hello, and welcome to the forum.

The interface requrements for the SHT11 humidity sensor have previously been discussed on this forum. The following thread also provides a link to an earlier thread containing additional information -

http://forums.freescale.com/freescale/board/message?board.id=8BITCOMM&message.id=4381

The sample code provided by Sensirion will need some adaption to suit the I/O of the Freescale device. Another issue might be the avoidance of floating point calculations, tor the calculation of temperature and humidity. Both these issues were discussed.

Regards,

Mac

Re: Configuration problem by using 13192SARD boards and the SHT11 humidity

psy — Tue, 18 Dec 2007 22:40:34 GMT

Thanks.And for the hardware configuration,if i want to use the PTB 0 and PTB 1,so i have to connect the DATA pin of the sensor to PTB 0 and SCK pin to PTB 1...It is true ??

Re: Configuration problem by using 13192SARD boards and the SHT11 humidity

bigmac — Wed, 19 Dec 2007 08:07:37 GMT

Hello,

You are correct. However, as explained in a previous thread, the control of the DATA line will need to differ from the sample code, for the HCS08 MCU to be compatible with SHT11 requirements - the DATA signal must never be driven high. This is achieved by controlling the DDR bit, rather than the port register bit.

For example,

Initialise DATA and CLOCK lines with -

PTBD_PTBD0 = 0; /* This setting not altered */

PTBDD_PTBDD1 = 1; /* CLOCK line is output */

Set DATA line low -

PTBDD_PTBDD0 = 1; /* Set pin for output */

Set DATA line high -

PTBDD_PTBDD0 = 0; /* Set pin for input/high-Z */

Set CLOCK line low -

PTBD_PTBD1 = 0;

Set CLOCK line high -

PTBD_PTBD1 = 1;

Regards,

Mac

Re: Configuration problem by using 13192SARD boards and the SHT11 humidity

psy — Fri, 28 Dec 2007 11:05:50 GMT

For the hardware configuration,if the sensor need 3V of VDD to operate,hw i can get the 3V of VDD from the 13192SARD board?Thanks

Re: Configuration problem by using 13192SARD boards and the SHT11 humidity

peg — Wed, 02 Jan 2008 05:20:36 GMT

Hi psy,

3 volts is available at J103.
It is marked J103 and 3V and + -.

Re: Configuration problem by using 13192SARD boards and the SHT11 humidity

psy — Sat, 05 Jan 2008 01:07:03 GMT

Hi,

If the sensor need 5V of VDD to operate,hw i can get the 5V of VDD from the 13192SARD board?Thanks

Re: Configuration problem by using 13192SARD boards and the SHT11 humidity

peg — Sun, 06 Jan 2008 19:11:10 GMT

Hi psy,
Well you can use the :smileyminus: pin from J103 and TP104 on the back is 5V. There is no easy way!

Re: Configuration problem by using 13192SARD boards and the SHT11 humidity

bigmac — Mon, 07 Jan 2008 00:18:01 GMT

Hello,

If you wish to operate the SHT11 sensor from Vdd = 5 volt, keep in mind that you will require the complication of additional buffering between the MCU and the sensor - a direct connection would unlikely be feasible.

For reliable operation, the minimum logic high input to the sensor needs to be greater than 4.0 volt, well above the output level provided by the MCU. To prevent damage to the MCU, the pull-up resistor on the data line would need to be sourced from the MCU Vdd.

There has been discussion of voltage comptibility issues in the following recent thread -

http://forums.freescale.com/freescale/board/message?board.id=8BITCOMM&thread.id=8640

Since the data line interface for the sensor requires an "open drain" configuration, the interface method will need to accommodate this requirement. Obvioulsy, it would be much simpler if the sensor Vdd is the same as that for the MCU.

Regards,

Mac