Barometer Pressure Module HOPE HP03

[Acetronics2]

Hi, Dave

I have a Barometer/Altimeter/Tempmeter/Clock with a 5534, running here ...

The Pic and the sensor are powered from a 3v regulator ( ICL 7663 )
32,7 Khz clock is derived from the PWM module of the PIC ( both 16F876 ( LCD 2x20 ) or 18F452 ( GLCD 122x32 ) projects ... )

The only thing to remember is to have a STRONG Decoupling of the sensor supply : 47µF + Tantalum is recommended for reliable work.

Alain

[Bill Legge]

Thanks for the infirmation.

It seems that the pins are NOT 5 Volt tolerant and I either:

1. Use the bi-directional level converting circuit given in the Philips application note, or
2. Run the MCU at 3 Volts.

Thanks for the idea of using the HPWM signal for the A/D clock.

The HP03 chip (mounted on a carrier with 0.1 inch pins) is available from Ocean Controls here in Australia for about $AUS 25 ($US 20): http://www.oceancontrols.com.au

Thanks Bill Legge

[Bill Legge]

Alain of Acertronics

Alain,

Thanks for your post. Any chance of seeing your program for the 5534. Particularly the I2C comms bit?

I've got mine running but the calibration coefficients are nothing like the published example. I'm wondering if:

1. My code is wrong, or
2. My level conversion is wrong?

Regards Bill Legge
In Australia

[Bill Legge]

Alain of Acertronics

Don't bother with the code - I've just got mine working.

Pull-up resistor on the SCL line was poorly connected.

The bi-directional level conversion described in the Philips application note works fine with a 2N7000 MOSFET.

Regards Bill Legge

[dhouston]

Thanks for the infirmation.

It seems that the pins are NOT 5 Volt tolerant and I either:

1. Use the bi-directional level converting circuit given in the Philips application note, or
2. Run the MCU at 3 Volts.

There are some simpler methods than those in the Philips app note. See Interfacing to Lower Voltage Devices on pp10-11 of http://www.zbasic.net/appNotes/AN213.pdf. The transistor (e.g. 2N3904) circuits of FIG 15 will work for nearly anything.

[BrianT]

I have used hundreds of intersema sensors for atmospheric pressure and 5 - 10 atmosphere applications over the last 5 years. I use a simple resistive divider for the 5>3v3 level conversion. In the 3v3>5 direction I just directly connect.

I run the PIC at 5 volts and the Intersems 5534 at 3v3 from an LDO 3 volt regulator. From PIC to 5534 I have 2k2 with 3k3 to ground at the 5534 end for signals to the 5534 DIn, SClk and MClk. DOut, from the 5534, I just hook directly to the PIC. Yes that means a 3v3 signal into a 5 volt PIC (RC.3). It works.

The HOPE is definitely a knock off of the Intersema product. Has anyone done any side by side accuracy tests? Pricing looks slightly in favour of the HOPE unit but I'm not going to make the change unless the accuracy is at least as good as the Swiss Intersema units.

Cheers
BrianT

[Bill Legge]

The circuit on the attached JPEG has been running well. At $25 a go for the HOPE HP03 I'm reluctant to risk the direct connection between the 3.3 and 5 Volt chips.

Regards Bill legge

[wjsmarine]

Hi Bill,

I use the same setup as BrianT however also add a 3v zener to ground on the data pin (cathode) and a series 220R resistor going to the 5v PIC, just in case...

Regards,
Bill