How can we help you?: on recent order, i attempted RTC and CO2 and OLED, SD card CO2 datalogger - with 3.7 v bat and battery level measurment enabled I was having trouble - could never see the RTC, but could read the CO2 - on the Qwiic. So removed ALL the sensors and did some measurementsā¦with all sensors unattached, 3v3 reads 3.3, 5v reads 4.95, both sides MEAS reads 4.95, "BAT+ reads 4.3, BAT- reads 0 all to ground.
it looks like the MEAS is attached to the 5v rail??? how is that possible??
The MEAS jumper is connected by default, to make use of it youāll sever the trace between the pads and solder 2 leads from whatever is performing the measurement to each side/pad
Thereās also a lipo fuel gauge on the board at i2c address 0x36 if that helps
Well, Gemini and I may have killed a couple RedBoards :o( more on that later, when i check them out more thoroughly - i cut the MEAS, and now an orange LED lights up briefly.
BUT on to the ānewā problem - i unwrapped a NEW RedBoard ESP32 IoT, hooked up RTC and RAN Sparkfun Example, 1 - TimeSet. It does NOT see RTC. So, I ran a simple I2C scanner, and it will see the CO2, OLED, pawerMax addresses and it sees the RTC as 0x69, not 32. There is no power light on the RTC. but there is one the CO2.
So I removed the RTC and i can read CO2, bat voltage and run off a 3.7v bat and/or USB. The code to do that pulls GPIO 5 HIGH to read I2C. Now I want to write to the onboard SD and it requires GPIO 5 pulled LOW to write to the SD. I previously found that the CS for SD card is NOT 10. I get this solution from Gemini AIā¦You are absolutely right to pause. We have arrived at the GPIO 5 Paradox, and if we arenāt careful, adding the SD card will kill the stability we just achieved.
The GPIO 5 Conflict (Refreshed)
As per the schematic, GPIO 5 on your RedBoard IoT is tied to two things:
SD_CS (Chip Select): The signal that tells the SD card āI am talking to you.ā
Peripheral Power Enable: The FET that turns on the 3.3V rail for your CO2 and OLED.
The Problem: The SD library usually pulls the CS pin LOW to start communication. On your board, pulling Pin 5 LOW cuts the power to your sensors.
The āSafeā Integration Strategy
To make this work without the bus crashing, we have to treat the SD card like a āguestā that briefly borrows the power line.
Hold HIGH by Default: We must keep Pin 5 HIGH at all times to keep the CO2 sensor and OLED alive.
The āPre-Flightā Check: We read the sensors first, then briefly open the SD card, write the data, and immediately close it so Pin 5 can return to HIGH.
When I bought these boards, I assumed that i could use the QWiic sensors and the BUILTIN SD card slot, but Im at a loss for how to use them together, without fancy āpin gymnasticsāā¦
Please advise me how to do this (use builtin SD card AND QWiic sensors), becauseā¦ GPIO_5 is hardwired ā¦.the physical traces on your SparkFun IoT RedBoard are permanently soldered from the ESP32 chip to the built-in SD slot using GPIO 5.
If you use the Built-in Slot: You are physically forced to use GPIO 5. No matter what you tell the code, the electricity still flows through that trace, which is also connected to the Power FET. Reassigning the pin in code wonāt āun-wireā the boardā¦
Re RTC, if i use an i3c scanner, RTC shows up as 0x69, but when i use the Sparkfun example in RV8803 library, it says RTC not foundā¦. so is th e library looking for the RTC on another address??
Upon checkingā¦ the *.h in libraryā¦
ā/The 7-bit I2C address of the RV8803 #define RV8803_ADDR 0x32ā
So, yes, the scanner finds it as 0x69, but the library is looking for 0x32ā¦ im not impressed.
EDIT::: I changed 0x32 to 0x69 in .h file and bam! RTC now working.
@YellowDog , ty re RTC, but GPIO 5 is still an issue, could you look belowā¦ GPIO 5 is hardwired to CS on SD and controls power on 3v3, so how can i use QWiic sensors AND the onboard SD card at the same time?
Iām not seeing in the schematic where GPIO5 controls power to anything. I2C power comes directly from the 3.3 volt supply and that should always be on.
I have seen some SD cards require a lot more current than the board expexts, those can cause a dip in voltage on the 3.3 volt bus and that could cause some I2C devices to reset or hang.
You might try a variety of SD cards and see if one works better than another.
A sketch that scans the I2C bus while performing read/writes to the SD card would be a good test for different cards to weed out problematic ones.
In your post above, you said you were using a RV-1805 RTC. Yet, in your later posts, you refer to the library for the RV-8803. Those are two similar but different devices:
RV-1805 has a shifted I2C address of 0xD2 / 0xD3 Hexadecimal. The actual unshifted address is 0x69 Hexadecimal = 105 decimal. (The unshifted address gets shifted left by one bit, to āmake roomā for the Read/!Write bit.)
I suggest you correct your posts, so you donāt mislead more readers.
Also, to echo @YellowDog 's comment, the IoT RedBoard ESP32 GPIO5 is connected to microSD CS and a breakout pad only. It does not control any part of the power circuit. AI has completely misled you there.
The GPIO 5 Conflict (Refreshed)
The āSafeā Integration Strategy
