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