TM4C1294NCPDT: SSI Master-Slave Example Not Working — Receiving Garbage Data

Part Number: TM4C1294NCPDT
Other Parts Discussed in Thread: EK-TM4C1294XL

Hi,

I am trying to run the TivaWare example spi_master_slave_xfer.c on the EK-TM4C1294XL LaunchPad, where SSI0 is configured as Master and SSI1 as Slave on the same board using jumper wires.

However, the example does not work as expected.

Issue

The UART output shows transmission messages correctly, but the received data is always garbage / blank:

SSI Master-Slave Transfer Example.
Mode: Legacy SPI
Data: 8-bit
 
SSI0 Sent:
  'T' 'I' 'V' 'A' 
SSI1 Sent:
  'Q' 'S' 'S' 'I' 
 
SSI0 Received:
  '' '' '' '' 
SSI1 Received:
  '' '' '' '' 
 
Master-Slave Transfer Complete.

Sometimes I also observe values like 0xFF or 0x00.

Hardware Connections (same board loopback)

I connected the pins exactly as per the example:

• PA2 (SSI0CLK) → PB5 (SSI1CLK)

• PA3 (SSI0FSS) → PB4 (SSI1FSS)

• PA4 (SSI0TX) → PE5 (SSI1RX)

• PA5 (SSI0RX) ← PE4 (SSI1TX)

• GND connected

No cross-board wiring, only jumper wires on the same LaunchPad.

Request

Could someone please share:

1. A confirmed working SPI Master-Slave example for TM4C1294XL (same board SSI0 ↔ SSI1)

2. Any known hardware or timing requirements not mentioned in the example

3. Whether manual CS control is required instead of hardware FSS

4. Any issue with SSI slave TX FIFO needing preload before clock