Webench and the TIDA-00056 for an H2S Sensor

Nicole,

I apologize for the delay here, but have you seen the LMP91000 Sensor AFE Designer (link below)? From there, it will open up a tutorial that you can watch, followed by a sensor selection page. Unfortunately the Synkera sensors aren't listed, but you can add it by clicking the "NEW" button labeled at the top of the page. I would start with this process for the hardware, then follow the user guide about updating the firmware using the CC debugger.

LMP91000 Webench: http://webench.ti.com/webench5/sensorafe/?part=LMP91000

Eval Board User Guide: http://www.ti.com/lit/ug/snoa922/snoa922.pdf

-Reagan

Nicole,

IAR is currently the only supported IDE for developing and debugging with the CC2541. Evaluation versions include a 30-day full-feature version, as well as a code-size limited one isn't time-limited.

While IAR is used for development, we also have the SmartRF evaluation applications shown on the CC2541 page under Software>Development Tools (see link below). Features of these applications include a packet sniffer, flash programmer, and register configuration.

http://www.ti.com/product/CC2541/toolssoftware

-Reagan

Hi

I was the original designer for the TIDA-00056. The person who can really help you answer the City tech sensors is Domenico.Granozio@ti.com. He is really familiar with these.

/Ajinder  

Hi,

the only hardware change in the TIDA-00056 to accomodate a 3-lead gas sensor (such as the H2S) is related to the resistor R43 which shorts the RE to CE of the LMP91000.

You have to remove that resistor, in this way the LMP91000 works as true potentiostat. The R43 resitor is used when 2-lead gas sensors (such as oxygen) are connected to the LMP91000.

regards,

Domenico

Thanks Domenico

This is explained in the users guide as well. Please let us know if there are any pending questions

While knowing that I will need to modify the TIDA-00056 electronically is helpful, it had nothing to do with my question.  According to the user manual (http://www.ti.com/lit/ug/snoa922/snoa922.pdf#page=12&zoom=auto,0,691.9) I am supposed to update the sensorservice.c file.

However, the Web bench (which is supposed to have those values is practically unpopulated).

Now either you are trying to tell me that the firmware needs no updating (in which I have been given the runaround to buy the debugger and to work with your firmware code) or there is information lacking to allow me to use your supposedly compatible hardware.

Lets make some easy questions then.

To use the H2S sensor from City tech the H2S 3E 100 with the Gas Sensor Platform known as the TIDA-00056 do I need to update the firmware?

If yes:

Where do I find the parameters for the Citytech H2S 3E 100 (and please don't say the data sheet because I've already looked there) to fulfill the parameters for the sensorservice.c file?

Do I need to remove Resistor 43 as was previously stated in your earlier email?

Please understand that I am trying to make the firmware work right now.  Though if there is anything else that had almost no mention that I should know about, it would also be helpful.

Best regards,

Nicole Stanton

Hi Nicole

Here are my responses. By default what we ship on e store has the firmware for 3 lead Amperoemetric Gas Sensor - like the CO sensor that we explain in the documentation.

The City Sensoric H2S is also 3 lead ampereometric so we dont need to change anything in the hardware. So to answer your question.

Do I need to remove Resistor 43 as was previously stated in your earlier email? >> No, the resistor is already removed as required for an ampereometric, so you dont need to do anything.

Now lets address the firmware questions: As by default we support Ampereometric, then if you refer to page 5 of the documentation (design guide) where I have equations, then as far as Vref_div go lets keep it same as 20% of Vref so it will be 0.5V. As the VREF is 2.5V

Lets keep the RTIA same as 7000 as the default firmware, now by this you DONT have to change anything in the firmware. The only concern I would have here is that the specification of the H2S sensor that you have, has its max current at full range (100ppm) would only produce a max voltage of 0.63V with a setting of 7000 RTIA setting.

I am taking (750nAppm+150nA/ppm)*100*7000 = 0.63V

So now your sensor range analog output would be from 0.5V (above) to 0.63V (very less dynamic range). Now if you can change the firmware to change RTIA to lets say 14kohms (page 14 of the LMP91000 datasheet) then you can get a dynamic range from 0.5V to 1.25V corresponding to 0ppm to 100ppm

You may have to make adjustments to the IOS app for proper display of ppm

Using the City Sensoric Data: The range is only 0-100pm as compared to 5000pom for the CO sensor

Domenico pls comment if you want to add anything

When I said change RTIA, i meant change TIA_GAIN (or the register 0x10) bit [4:2] to 100

You dont have to change RLOAD

Nicole

You should be able to change the ppm scale in the app itself. Let me know if you still have any questions.

/Ajinder

Ajinder,

I'm sorry to say that I am at my wits end.  for the life of me I cannot understand what I'm doing wrong however when I put the sensor in testing I cannot get a reading on any H2S.  Are there limitations to the TIDA-00056?  the sensor I am using is 0-100ppm H2S and I am testing it with 5ppm premixed certified gas.  Please advise.

Nicole Stanton

Hi Nicole

What I recommend is that you first try and look at the output voltage (analog output of the LMP91000)with an oscilloscope and see if it is changing in the environment. Please note that the iOS app may need adjustment for the ppm reading.

You need to probe on pin 8 of the LMP91000 device or U5

But key would be to first see that if the analog output voltage is changing as you change the H2S environment.

/Ajinder