7 Replies Latest reply on Jun 14, 2017 7:10 AM by epr_1639216

    CE211252 Ambient Light Sensor Example Warnings

      I was experimenting with the example project from the CY8CKIT-048 development board. I've got some odd warnings that I can't seem to find information about:

      • Opamp \Opamp_TIA:cy_psoc4_abuf\ output pin TIA_OUT(0) is fixed in an incompatible location [IOP=(2)][IoId=(4)]
      • The pin named TIA_IN(0) at location [IOP=(2)][IoId=(3)] prevents usage of special purposes: F(OA,1).

      I was going to make some changes and when I cleaned and rebuilt the project I noticed these warnings even after I disables the components I added.




      I've attached the project.

        • 1. Re: CE211252 Ambient Light Sensor Example Warnings

          Hi George,

          You have interchanged the TIA_IN and TIA_OUT pins in the design. The opamp has dedicated pins for input and output and you have to use them. So now another opamp is being used due to routing restriction. And this opamap is not connected to the pins you are using. You can see this on CYDWR-> analog tab. If you interchange 2[3] and 2[4] pins the warning should disappear and correct device will be selected.

          Best Regards,

          • 2. Re: CE211252 Ambient Light Sensor Example Warnings

            Hi Vasanth,


            I'm a little confused by your statement "The opamp has dedicated pins for input and output and you have to use them." What is determining that the opamp has dedicated pins? I thought we could move pins and these come up as warnings and not errors.


            I was trying to add a photodiode to this board and check it's characteristics compared to the onboard ALS. I was looking at the board schematic and found that P3.0 and P3.1 were not connected to any circuit so I was trying to use those pins. Where could I add my photodiode on this board so I can use the same circuit (except for the external filter, R84=220k and C58=0.1uF) in this project example?


            Best Regards,



            • 3. Re: CE211252 Ambient Light Sensor Example Warnings

              Hi George,

              Sorry for the lack of clarity. The Opamp has dedicated inputs and output pins. For input there are options to route as AMUX bus, so routing is possible. But for output pins it directly routed to dedicated pin. So when you use the output pin of an opamp component for some other purpose it will cause routing issues. The pin 2[3] is dedicated output pin of F(OA,1) opamp. Once you use 2[3] as a input to the Opamp, F(OA,1) module cannot be used. So the design places a different opamp  F(OA,3). To get a visual idea of what I am saying go to CYDWR window and  see analog tab. You can hover over the opamp components and see the naming. Routings from input and output can be also seen,

              One more clarification, using different pins won't prevent your normal operation. ie even though the warnings are popping up, the circuit will work as you expect. But it is better if you can use the dedicated pins. It will avoid unwanted routing and resistance due to that if your application is sensitive to that. 

              Best Regards,

              • 4. Re: CE211252 Ambient Light Sensor Example Warnings

                Hi VSRS,


                I looked through the Getting Started with PSoC® Analog Coprocessor app note and the PSoC® Analog Coprocessor: CY8C4Axx Family Datasheet and I don't see any mention about having the outputs "fixed" to P2.3. I understand what you're saying about looking at the analog tab to see the routing but compared to other PSoC devices this seems rather confusing to me. 

                • 5. Re: CE211252 Ambient Light Sensor Example Warnings

                  There are physically only so many wires/connections to the hardware (like to the input/output pins of the op-amps). Using alot of compiler magic and mesh wiring, they make it seemless to the user, but essentially there is a giant mux and demux connecting all devices on the board, with the mux/demux being limited to a fixed number of routes using specific pins. (It's similar to routing traffic through roads in a city) Even though you can route the pins between the components, there are limitations to which hardware can use which pins/routes (not always, but for pick/choose cases). Using the traffic analog: Traveling from point A to B will be possible with multiple routes, but each one will be using different wires (streets), and preventing other routes from using those same wires (streets). Each hardware peripheral (op-amp in this case) has a fixed number of streets bordering it (pretend it can be more/less than four ;) ), thus preventing how many routes are available for each hardware peripheral (building). Even though all of the streets exist in the same chip (city), you will have to use specific wires (streets) to connect to specific peripherals (buildings). This leads to collisions in routing as you use more resources (routes/streets). Thus, once you reach a higher number of in-use routes, you will have to start routing wires (streets) through long circuits with negative side-effects; Higher capacitance/resistance (more stop lights), longer signal (travel) time, etc.

                  • 6. Re: CE211252 Ambient Light Sensor Example Warnings

                    Thanks, I understand the routing portion but I don't see where this is detailed in documentation. I've used PSoC devices on and off over the years but this the first time I've seen a mention of "Opamp, F(OA,1)" and having things "fixed" to physical pins. I know things just can't go anywhere but it seems like I'm missing some documentation on what's possible. I was hoping to add a photodiode to this board and compare my results to the onboard ALS but it's not looking like that's really possible.

                    • 7. Re: CE211252 Ambient Light Sensor Example Warnings

                      Yeah, I've not seen mention of it either. The closest I've seen to documentation on the hardware routing/connections is in the "Analog" tab of the PSoC creator, which shows the hardware peripherals and pins, and the routes used/available.