Update data in/out pin swap on MCU #4

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opened 2026-03-17 21:30:24 +00:00 by allspice-carah · 0 comments

allspice-carah commented

2026-03-17 21:30:24 +00:00

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Component J4, pins 6, 8: TDO and TDI signals are swapped. Pin 6 (TDO/SWO) is incorrectly connected to the microcontroller's TDI pin (PB29), and pin 8 (TDI) is incorrectly connected to the microcontroller's TDO pin (PB30). This will prevent JTAG debugging from functioning.

Pin 6 is connected to the TDO/SWO net (from schematic)
Pin 8 is connected to the TDI net (from schematic)
The TDO/SWO net connects to U11A pin 29 which is labeled PB29/TDI (from schematic)
The TDI net connects to U11A pin 30 which is labeled PB30/TDO/TRACESWO (from schematic)
ARM Cortex Debug Connector standard specifies pin 6 as TDO/SWO (Test Data Out / Serial Wire Output) and pin 8 as TDI (Test Data In) (reasoning)
In JTAG operation, TDO is an output from the target device and TDI is an input to the target device (reasoning)
The microcontroller pin 29 (PB29) is the TDI function (input to MCU) and pin 30 (PB30) is the TDO function (output from MCU) per standard ARM Cortex-M3 implementations (reasoning)
The connections are swapped: J4 pin 6 should connect to MCU TDO (pin 30) but connects to MCU TDI (pin 29), and J4 pin 8 should connect to MCU TDI (pin 29) but connects to MCU TDO (pin 30) (reasoning)
The presence of pull-up resistor R37 on the net labeled TDI (which actually connects to MCU TDO) is unusual, as TDI typically doesn't require a pull-up while TDO might benefit from one, further suggesting the swap (reasoning)
To correct this error, the TDO/SWO net should be connected to U11A pin 30 (PB30/TDO/TRACESWO) and the TDI net should be connected to U11A pin 29 (PB29/TDI) (reasoning)

All affected pins

Component U11A, pins `29, 30`: JTAG data pins TDI and TDO are swapped. Pin 29 (TDI) connects to TDO/SWO net, and pin 30 (TDO) connects to TDI net.

Pin 29 is PB29/TDI (Test Data In) (from schematic)
Pin 29 is connected to net TDO/SWO (from schematic)
Pin 30 is PB30/TDO/TRACESWO (Test Data Out) (from schematic)
Pin 30 is connected to net TDI (from schematic)
PB29 should function as TDI (Test Data In) per datasheet (from datasheet ATSAM3X8EA-AU, page 8)
PB30 should function as TDO/TRACESWO (Test Data Out) per datasheet (from datasheet ATSAM3X8EA-AU, page 8)
JTAG connector J4 pin 6 connects to net TDO/SWO, which should go to pin 30 (TDO) (from schematic)
JTAG connector J4 pin 8 connects to net TDI, which should go to pin 29 (TDI) (from schematic)
The TDI and TDO pins are swapped, preventing proper JTAG debugging (reasoning)
Pin 29 should connect to net TDI, and pin 30 should connect to net TDO/SWO (reasoning)

Component J4, pins `6, 8`: TDO and TDI signals are swapped. Pin 6 (TDO/SWO) is incorrectly connected to the microcontroller's TDI pin (PB29), and pin 8 (TDI) is incorrectly connected to the microcontroller's TDO pin (PB30). This will prevent JTAG debugging from functioning.

Pin 6 is connected to the TDO/SWO net (from schematic)
Pin 8 is connected to the TDI net (from schematic)
The TDO/SWO net connects to U11A pin 29 which is labeled PB29/TDI (from schematic)
The TDI net connects to U11A pin 30 which is labeled PB30/TDO/TRACESWO (from schematic)
ARM Cortex Debug Connector standard specifies pin 6 as TDO/SWO (Test Data Out / Serial Wire Output) and pin 8 as TDI (Test Data In) (reasoning)
In JTAG operation, TDO is an output from the target device and TDI is an input to the target device (reasoning)
The microcontroller pin 29 (PB29) is the TDI function (input to MCU) and pin 30 (PB30) is the TDO function (output from MCU) per standard ARM Cortex-M3 implementations (reasoning)
The connections are swapped: J4 pin 6 should connect to MCU TDO (pin 30) but connects to MCU TDI (pin 29), and J4 pin 8 should connect to MCU TDI (pin 29) but connects to MCU TDO (pin 30) (reasoning)
The presence of pull-up resistor R37 on the net labeled TDI (which actually connects to MCU TDO) is unusual, as TDI typically doesn't require a pull-up while TDO might benefit from one, further suggesting the swap (reasoning)
To correct this error, the TDO/SWO net should be connected to U11A pin 30 (PB30/TDO/TRACESWO) and the TDI net should be connected to U11A pin 29 (PB29/TDI) (reasoning)

Datasheets: 📄 J4 📄 U11A

_{Replace a datasheet: 📤 J4 📤 U11A}

Originally posted by @DRCY in https://hub.allspice.io/AllSpice-Demos/Archimajor-DRCY-Demo/pulls/2/files#diff-a1cf5d09dc90c04322d148737a149dcd67c7492b-issuecomment-44849

**Component `J4`, pins `6, 8`: TDO and TDI signals are swapped. Pin 6 (TDO/SWO) is incorrectly connected to the microcontroller's TDI pin (PB29), and pin 8 (TDI) is incorrectly connected to the microcontroller's TDO pin (PB30). This will prevent JTAG debugging from functioning.** !thumbnail[](Microcontroller.SchDoc){ diff="AllSpice-Demos/Archimajor-DRCY-Demo:26590581be02618ce3f47deedb643c2d47d4182d...b09435216bda90650e7fdf6b009674871e52ddc7" pr="2" diff-visibility="full" variant="default" view-coords="39.19,70.36,46.69,78.76" aspect-ratio="1.55" } - Pin 6 is connected to the TDO/SWO net *(from schematic)* - Pin 8 is connected to the TDI net *(from schematic)* - The TDO/SWO net connects to U11A pin 29 which is labeled PB29/TDI *(from schematic)* - The TDI net connects to U11A pin 30 which is labeled PB30/TDO/TRACESWO *(from schematic)* - ARM Cortex Debug Connector standard specifies pin 6 as TDO/SWO (Test Data Out / Serial Wire Output) and pin 8 as TDI (Test Data In) *(reasoning)* - In JTAG operation, TDO is an output from the target device and TDI is an input to the target device *(reasoning)* - The microcontroller pin 29 (PB29) is the TDI function (input to MCU) and pin 30 (PB30) is the TDO function (output from MCU) per standard ARM Cortex-M3 implementations *(reasoning)* - The connections are swapped: J4 pin 6 should connect to MCU TDO (pin 30) but connects to MCU TDI (pin 29), and J4 pin 8 should connect to MCU TDI (pin 29) but connects to MCU TDO (pin 30) *(reasoning)* - The presence of pull-up resistor R37 on the net labeled TDI (which actually connects to MCU TDO) is unusual, as TDI typically doesn't require a pull-up while TDO might benefit from one, further suggesting the swap *(reasoning)* - To correct this error, the TDO/SWO net should be connected to U11A pin 30 (PB30/TDO/TRACESWO) and the TDI net should be connected to U11A pin 29 (PB29/TDI) *(reasoning)* <details> <summary>All affected pins</summary> <details> <summary>Component <code>U11A</code>, pins `29, 30`: JTAG data pins TDI and TDO are swapped. Pin 29 (TDI) connects to TDO/SWO net, and pin 30 (TDO) connects to TDI net.</summary> - Pin 29 is PB29/TDI (Test Data In) *(from schematic)* - Pin 29 is connected to net TDO/SWO *(from schematic)* - Pin 30 is PB30/TDO/TRACESWO (Test Data Out) *(from schematic)* - Pin 30 is connected to net TDI *(from schematic)* - PB29 should function as TDI (Test Data In) per datasheet *(from datasheet [ATSAM3X8EA-AU](<https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdf#page=8>), page 8)* - PB30 should function as TDO/TRACESWO (Test Data Out) per datasheet *(from datasheet [ATSAM3X8EA-AU](<https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdf#page=8>), page 8)* - JTAG connector J4 pin 6 connects to net TDO/SWO, which should go to pin 30 (TDO) *(from schematic)* - JTAG connector J4 pin 8 connects to net TDI, which should go to pin 29 (TDI) *(from schematic)* - The TDI and TDO pins are swapped, preventing proper JTAG debugging *(reasoning)* - Pin 29 should connect to net TDI, and pin 30 should connect to net TDO/SWO *(reasoning)* </details> <details> <summary>Component <code>J4</code>, pins `6, 8`: TDO and TDI signals are swapped. Pin 6 (TDO/SWO) is incorrectly connected to the microcontroller's TDI pin (PB29), and pin 8 (TDI) is incorrectly connected to the microcontroller's TDO pin (PB30). This will prevent JTAG debugging from functioning.</summary> - Pin 6 is connected to the TDO/SWO net *(from schematic)* - Pin 8 is connected to the TDI net *(from schematic)* - The TDO/SWO net connects to U11A pin 29 which is labeled PB29/TDI *(from schematic)* - The TDI net connects to U11A pin 30 which is labeled PB30/TDO/TRACESWO *(from schematic)* - ARM Cortex Debug Connector standard specifies pin 6 as TDO/SWO (Test Data Out / Serial Wire Output) and pin 8 as TDI (Test Data In) *(reasoning)* - In JTAG operation, TDO is an output from the target device and TDI is an input to the target device *(reasoning)* - The microcontroller pin 29 (PB29) is the TDI function (input to MCU) and pin 30 (PB30) is the TDO function (output from MCU) per standard ARM Cortex-M3 implementations *(reasoning)* - The connections are swapped: J4 pin 6 should connect to MCU TDO (pin 30) but connects to MCU TDI (pin 29), and J4 pin 8 should connect to MCU TDI (pin 29) but connects to MCU TDO (pin 30) *(reasoning)* - The presence of pull-up resistor R37 on the net labeled TDI (which actually connects to MCU TDO) is unusual, as TDI typically doesn't require a pull-up while TDO might benefit from one, further suggesting the swap *(reasoning)* - To correct this error, the TDO/SWO net should be connected to U11A pin 30 (PB30/TDO/TRACESWO) and the TDI net should be connected to U11A pin 29 (PB29/TDI) *(reasoning)* </details> </details> Datasheets: [📄 J4](https://cdn.amphenol-cs.com/media/wysiwyg/files/documentation/datasheet/boardwiretoboard/bwb_minitek127_btb.pdf) [📄 U11A](https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdf) <sub>Replace a datasheet: [📤 J4](https://hub.allspice.io/AllSpice-Demos/Archimajor-DRCY-Demo/_upload/develop/.allspice/datasheets/20021121-00010C4LF) [📤 U11A](https://hub.allspice.io/AllSpice-Demos/Archimajor-DRCY-Demo/_upload/develop/.allspice/datasheets/ATSAM3X8EA-AU)</sub> _Originally posted by @DRCY in https://hub.allspice.io/AllSpice-Demos/Archimajor-DRCY-Demo/pulls/2/files#diff-a1cf5d09dc90c04322d148737a149dcd67c7492b-issuecomment-44849_