I'm trying to diagnose an iPhone 6s that's stuck in a boot loop. iTunes error points to a baseband issue.
So I've compared to a known working board and found that the PMU_TO_BB_PMIC_RESET_L line (at Resistor R2200) should be high at 1.8v but when I measure it's very momentary high then quickly drops and stays low at 0v
Tracing the line it's an out from the GPIO section of the main power ic for the entire phone
I have no other literature or information on how the circuit's supposed to function so I'm here asking to hopefully gather any information that may help me determine what's going on
If GPIO outputs are software controlled then I need to figure out what parameters are causing it to go low and stay low
So I've compared to a known working board and found that the PMU_TO_BB_PMIC_RESET_L line (at Resistor R2200) should be high at 1.8v but when I measure it's very momentary high then quickly drops and stays low at 0v
Tracing the line it's an out from the GPIO section of the main power ic for the entire phone
I have no other literature or information on how the circuit's supposed to function so I'm here asking to hopefully gather any information that may help me determine what's going on
If GPIO outputs are software controlled then I need to figure out what parameters are causing it to go low and stay low
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