If you investigate the unknown PCB without any circuit diagram - it needs to detect what GPIO is used for LEDs, or relay or other activity part.
Let's try:
1. Determine the MCU
2. Find the list of the MCU pins: note, if some danger (strapping) pin is in the list - MCU can just restart during the pins initialization.
3. Serial UART interface is not always available, it can be availabe only, say, at powering up with the pressed BOOT-button (GPIO0 at ESP32-family of MCU) - so the Morse code will help
4. After start be ready to press the BOOT button when you catch the LED blink or relay click: the sketch will hold the latest used GPIO number after you pressed the button. And next will blink it by the Morse code.
Let's try:
1. Determine the MCU
2. Find the list of the MCU pins: note, if some danger (strapping) pin is in the list - MCU can just restart during the pins initialization.
3. Serial UART interface is not always available, it can be availabe only, say, at powering up with the pressed BOOT-button (GPIO0 at ESP32-family of MCU) - so the Morse code will help
4. After start be ready to press the BOOT button when you catch the LED blink or relay click: the sketch will hold the latest used GPIO number after you pressed the button. And next will blink it by the Morse code.
B4X:
#Region Project Attributes
#AutoFlushLogs: True
#CheckArrayBounds: True
#StackBufferSize: 300
#End Region
'Sketch for testing MCU ports with output of port number in Morse code
Sub Process_Globals
Public Serial1 As Serial
'Active level configuration
Public const ACTIVE_HIGH As Boolean = False 'true - active level HIGH, false - active level LOW
'List of ports to test (excluding strapping pins and GPIO0), setup for your MCU
Public testPins() As Byte = Array As Byte(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 45, 46, 47, 48)
Public numTestPins As Int
Dim pinButton As Pin
Public const buttonPin As Byte = 0 'Button on GPIO0
Public const pinActivationTime As ULong = 300 '300ms port activation time for visibility
Public const pauseTime As ULong = 2000 '2 seconds pause for manual button clicking when seen the activity
Public selectedLedPin As Int = -1 'Memorized LED port
Public buttonPressed As Boolean = False
'Logging counters
Private testCycleCount As Int = 0
End Sub
Private Sub AppStart
Serial1.Initialize(115200)
Delay(3000)
Log("=== ESP32-S3 Port Testing Utility ===")
Log("Initializing...")
Log("Active Level: ", IIf(ACTIVE_HIGH, "HIGH", "LOW"))
Log("Number of test pins: ", testPins.Length)
Log("Button pin: GPIO", buttonPin)
Log("Starting in 5 seconds...")
numTestPins = testPins.Length
'Initialize all test ports as OUTPUT
Log("Initializing GPIO pins as OUTPUT...")
For i = 0 To numTestPins - 1
Dim p As Pin
p.Initialize(testPins(i), p.MODE_OUTPUT)
setPinState(testPins(i), False) 'Turn off all ports
Log("GPIO ", testPins(i), " initialized")
Next
'Button initialization
pinButton.Initialize(buttonPin, pinButton.MODE_INPUT_PULLUP)
Log("Button initialized on GPIO", buttonPin)
'5 second pause after start
Delay(5000)
Log("=== Starting port testing sequence ===")
'Main loop
Do While True
'If port is not yet selected, perform testing
If selectedLedPin = -1 Then
testCycleCount = testCycleCount + 1
Log("--- Test Cycle #", testCycleCount, " ---")
testAllPins
Else
Log("=== PORT SELECTED: GPIO", selectedLedPin, " ===")
Log("Starting Morse code transmission...")
'Blink the selected port number in Morse code
sendNumberMorse(selectedLedPin)
Log("Morse transmission completed. Pausing for 10 seconds...")
Delay(10000) '10 second pause between repetitions
End If
Loop
End Sub
Sub testAllPins
For i = 0 To numTestPins - 1
Dim currentPin As Byte = testPins(i)
Log("Testing GPIO", currentPin, " (", i + 1, "/", numTestPins, ")")
'Activate port
setPinState(currentPin, True)
Log("GPIO", currentPin, " ACTIVATED")
'Wait for activation time with button polling
Dim startTime As ULong = Millis
Dim buttonCheckCount As Int = 0
Do While Millis - startTime < pinActivationTime
checkButton(currentPin)
If buttonPressed Then
Log("BUTTON PRESSED DETECTED during activation!")
Exit
End If
buttonCheckCount = buttonCheckCount + 1
Delay(10)
Loop
'Deactivate port
setPinState(currentPin, False)
Log("GPIO", currentPin, " DEACTIVATED")
'If button is pressed, interrupt testing
If buttonPressed Then
Log("=== TESTING INTERRUPTED ===")
Log("Selected port: GPIO", selectedLedPin)
Log("Pausing for 5 seconds before Morse transmission...")
Delay(5000) '5 second pause
Return
End If
'Pause between ports
Log("Pausing for ", pauseTime, "ms...")
startTime = Millis
buttonCheckCount = 0
Do While Millis - startTime < pauseTime
checkButton(currentPin)
If buttonPressed Then
Log("BUTTON PRESSED DETECTED during pause!")
Exit
End If
buttonCheckCount = buttonCheckCount + 1
Delay(10)
Loop
If buttonPressed Then
Log("=== TESTING INTERRUPTED ===")
Log("Selected port: GPIO", selectedLedPin)
Log("Pausing for 5 seconds before Morse transmission...")
Delay(5000) '5 second pause
Return
End If
Log("GPIO", currentPin, " test completed")
Next
Log("--- Cycle #", testCycleCount, " completed ---")
End Sub
Sub checkButton(currentPin As Byte)
If pinButton.DigitalRead = False Then 'Button pressed (LOW due to PULLUP)
Log("[BUTTON] Initial press detected on GPIO", currentPin)
Delay(50) 'Debounce
If pinButton.DigitalRead = False Then 'still pressed
selectedLedPin = currentPin
buttonPressed = True
Log("[BUTTON] CONFIRMED - GPIO", currentPin, " selected!")
Log("[BUTTON] Button pressed: ", buttonPressed)
Log("[BUTTON] Selected LED pin: ", selectedLedPin)
Else
Log("[BUTTON] Debounce failed - false trigger")
End If
End If
End Sub
Sub sendNumberMorse(number As Int)
Log("[MORSE] Transmitting number: ", number)
'Split number into digits and transmit them sequentially
If number < 10 Then
'Single-digit number
Log("[MORSE] Single digit: ", number)
sendDigitMorse(number, selectedLedPin)
Else
'Two-digit number - transmit first digit, then second
Dim firstDigit As Int = number / 10
Dim secondDigit As Int = number Mod 10
Log("[MORSE] Two digits: ", firstDigit, " and ", secondDigit)
sendDigitMorse(firstDigit, selectedLedPin)
Log("[MORSE] Pause between digits...")
Delay(2000) 'Pause between digits (2 seconds)
sendDigitMorse(secondDigit, selectedLedPin)
End If
Log("[MORSE] Transmission completed for number: ", number)
End Sub
Sub sendDigitMorse(digit As Int, pin As Byte)
Log("[MORSE] Sending digit: ", digit, " on GPIO", pin)
Select digit
Case 0 ' -----
Log("[MORSE] Digit 0: -----")
dash(pin): dash(pin): dash(pin): dash(pin): dash(pin)
Case 1 ' .----
Log("[MORSE] Digit 1: .----")
dot(pin): dash(pin): dash(pin): dash(pin): dash(pin)
Case 2 ' ..---
Log("[MORSE] Digit 2: ..---")
dot(pin): dot(pin): dash(pin): dash(pin): dash(pin)
Case 3 ' ...--
Log("[MORSE] Digit 3: ...--")
dot(pin): dot(pin): dot(pin): dash(pin): dash(pin)
Case 4 ' ....-
Log("[MORSE] Digit 4: ....-")
dot(pin): dot(pin): dot(pin): dot(pin): dash(pin)
Case 5 ' .....
Log("[MORSE] Digit 5: .....")
dot(pin): dot(pin): dot(pin): dot(pin): dot(pin)
Case 6 ' -....
Log("[MORSE] Digit 6: -....")
dash(pin): dot(pin): dot(pin): dot(pin): dot(pin)
Case 7 ' --...
Log("[MORSE] Digit 7: --...")
dash(pin): dash(pin): dot(pin): dot(pin): dot(pin)
Case 8 ' ---..
Log("[MORSE] Digit 8: ---..")
dash(pin): dash(pin): dash(pin): dot(pin): dot(pin)
Case 9 ' ----.
Log("[MORSE] Digit 9: ----.")
dash(pin): dash(pin): dash(pin): dash(pin): dot(pin)
End Select
Log("[MORSE] Digit ", digit, " transmission completed")
End Sub
Sub dot(pin As Byte)
Log("[MORSE] DOT on GPIO", pin)
setPinState(pin, True)
Delay(500) 'Dot - 500ms
setPinState(pin, False)
Delay(500) 'Pause between dots/dashes
End Sub
Sub dash(pin As Byte)
Log("[MORSE] DASH on GPIO", pin)
setPinState(pin, True)
Delay(2000) 'Dash - 2000ms
setPinState(pin, False)
Delay(500) 'Pause between dots/dashes
End Sub
'Procedure to set port state considering active level
Sub setPinState(pin As Byte, state As Boolean)
Dim p As Pin
p.Initialize(pin, p.MODE_OUTPUT)
If ACTIVE_HIGH Then
p.DigitalWrite(state)
Else
p.DigitalWrite(Not(state))
End If
End Sub