Hardware Access Guide

Detailed guide for JTAG access to the Smartap device.

Safety First

Electrical Safety

The device operates at mains voltage. Always disconnect power before opening the device or making any connections.

Water Environment

This device is installed in a wet environment. Ensure all seals are properly reinstated after modification to prevent water ingress.

Opening the Device

Tools Needed

• Small Phillips screwdriver
• Plastic spudger or opening tool
• Anti-static wrist strap (recommended)

Procedure

1. Disconnect power - Turn off the circuit breaker for your bathroom
2. Remove control panel - Carefully detach the front control panel
3. Access main unit - Remove screws securing the main enclosure
4. Remove shielding - Carefully remove RF shielding if present
5. Locate JTAG header - Find the 6-pin unpopulated header

Take Photos

Take photos at each step to help with reassembly. Document the position of all cables and connections.

JTAG Interface

Header Location

The CC3200 module has a 6-pin vertical header labeled with pin 1 marked by a dot (●) and "+" symbol.

Pin 1  [●] +        ← Pin 1 marker
Pin 2  [ ]
Pin 3  [ ]
Pin 4  [ ]
Pin 5  [ ]
Pin 6  [■] GND      ← Ground

Pin Identification

Confirmed via JTAGenum:

Pin	Function	Description
1	NC	Not connected
2	TDO	Test Data Out
3	TCK	Test Clock
4	TMS	Test Mode Select
5	TDI	Test Data In
6	GND	Ground

IR Length: 6 bits

Connection Options

Option 1: Direct Wire Connection (Temporary)

Pros: - No soldering required - Reversible - Quick setup

Cons: - Unreliable connection - May disconnect during use - Requires holding in place

Method: Use female-to-female jumper wires, press firmly onto pads

Option 2: Soldered Pin Headers (Permanent)

Pros: - Reliable connection - Professional result - Easy reconnection later

Cons: - Requires soldering skills - Permanent modification - More time consuming

Method:

1. Obtain 2.54mm pitch pin headers
2. Cut to 6-pin length
3. Position headers in holes
4. Solder each pin carefully
5. Trim excess length if needed

Soldering Advice

Use a fine-tipped soldering iron (15-30W) and thin solder. Work quickly to avoid heat damage to the board. If inexperienced, practice on scrap electronics first.

Option 3: IC Test Clip

Pros: - No soldering needed - Secure connection - Reusable

Cons: - Requires suitable clip - May not fit all board layouts - Additional cost

Raspberry Pi Connection

GPIO Pinout

Connect Smartap JTAG to Raspberry Pi GPIO header:

Smartap        Wire Color      RPI GPIO        RPI Pin
Pin 2 (TDO)    [Suggested:     GPIO 26         Pin 37
Pin 3 (TCK)     Red/Blue/      GPIO 13         Pin 33
Pin 4 (TMS)     etc for        GPIO 19         Pin 35
Pin 5 (TDI)     easy           GPIO 6          Pin 31
Pin 6 (GND)     reference]     GND             Pin 39

Physical Setup

1. Power off everything - Both Smartap and Raspberry Pi
2. Connect wires - Attach jumpers to Raspberry Pi first
3. Connect to Smartap - Carefully attach other end to Smartap
4. Verify connections - Double-check every pin
5. Power on Raspberry Pi - Boot the Pi first
6. Power on Smartap - Then power on Smartap

Connection Order

Always connect wires with power OFF. Never hot-plug JTAG connections as this can damage both devices.

Connection Verification

Use a multimeter to verify:

1. Continuity - Each wire properly connected
2. No shorts - No accidental connections between pins
3. Ground - GND connection solid

Testing JTAG Connection

Install Software

# Update package list
sudo apt-get update

# Install OpenOCD
sudo apt-get install openocd

# Install GDB for ARM
sudo apt-get install gdb-multiarch
# Or ARM-specific:
sudo apt-get install gcc-arm-none-eabi gdb-arm-none-eabi

JTAGenum Test (Optional)

If you want to verify pin assignments:

# Clone JTAGenum
git clone https://github.com/cyphunk/JTAGenum.git
cd JTAGenum

# Edit header to set pins
nano JTAGenum.sh
# Set: pins=(26 19 13 6 5)
# Set: pinnames=(26 19 13 6 5)

# Run scan
source JTAGenum.sh
scan

Expected output:

FOUND!  ntrst:5 tck:13 tms:19 tdo:26 tdi:6 IR length: 6

OpenOCD Configuration

Create configuration files (see Research Background for complete configs):

sysfsgpio-smartap.cfg:

adapter driver sysfsgpio
sysfsgpio jtag_nums 13 19 6 26
sysfsgpio trst_num 5
adapter speed 100
reset_config trst_only

cc3200-complete.cfg: See full configuration in research background documentation.

Test Connection

cd /path/to/configs
openocd -f ./sysfsgpio-smartap.cfg \
        -c "transport select jtag" \
        -c "bindto 0.0.0.0" \
        -f ./cc3200-complete.cfg

Success looks like:

Info : Listening on port 4444 for telnet connections
Info : Listening on port 3333 for gdb connections
Info : JTAG tap: cc32xx.jrc tap/device found
Info : cc32xx.cpu: hardware has 6 breakpoints, 4 watchpoints

If it fails: - Check all connections - Verify power to both devices - Try slower speed: adapter speed 50 - Check GPIO permissions: Add user to gpio group

Memory Access

Once OpenOCD is running, connect via telnet:

telnet localhost 4444

Try basic commands:

> halt
> reg
> mdw 0x20004000 16
> resume

Troubleshooting

"Error: JTAG scan chain interrogation failed"

Causes: - Wires not connected properly - Wrong GPIO pins configured - Device not powered on - JTAG disabled in device fuses

Solutions: - Recheck all connections with multimeter - Verify pin numbers in config file - Ensure Smartap has power - Try different JTAG speed

"Cannot access memory at address 0x..."

Causes: - Device not halted - Watchdog timer reset device - Invalid memory address

Solutions: - Issue halt command first - Check watchdog handling in config - Verify address is valid for CC3200

Unstable Connection

Causes: - Poor physical connection - Wire too long - Electrical interference - Incorrect speed setting

Solutions: - Solder header pins for reliable connection - Use shorter wires (<20cm) - Keep wires away from power supplies - Reduce JTAG speed: adapter speed 50

Device Keeps Resetting

Causes: - Watchdog timer not being serviced - Power issue - JTAG configuration problem

Solutions: - Ensure watchdog handling in OpenOCD config - Check power supply stability - Verify reset configuration

Advanced: Manual Pin Finding

If you don't have documentation and need to find JTAG pins manually:

1. Visual inspection - Look for unpopulated headers near MCU
2. Continuity test - Trace pins to MCU if visible
3. JTAGenum scan - Systematically test pin combinations
4. Try standard TI layouts - CC3200 has common JTAG arrangements

Closing the Device

After JTAG work:

1. Verify functionality - Test device works before closing
2. Photograph setup - Document for future access
3. Label wires - If leaving wires attached, label clearly
4. Replace shielding - Reinstall RF shielding carefully
5. Check seals - Ensure water seals intact
6. Secure enclosure - Replace all screws properly
7. Test operation - Full functional test before closing walls

Water Sealing

This is critical! The device will be in a humid bathroom environment. Ensure all seals are properly reinstated to prevent water damage.

Resources

• CC3200 Datasheet
• OpenOCD Documentation
• JTAGenum Project
• Home Assistant Community Discussion - Includes photos of JTAG header

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