nrf52 spi reads extra zero

[Matts]

Hi.

I'm using nrf52 as slave for another device. I'm reading test string from the nrf buffer and I can see extra zero (rest of the content is then offset by one -> corruption). However I cannot see this extra clock in the bus when I check it with scope.

The data should be:

0x6a (0110 1010)
0x65 (0110 0101)
0x73 (0111 0011)

however in the buffer it's

0x35 (0011 0101)
0x32 (0011 0010)
0xb9 (1011 1001)

As you can see there's extra 0 and offset. In below scope picture there's only one zero.

nrf52 setup as follows:

• SPIS0 enabled and used with default config
• CS used
• SPIS clock mode is 0 (default, so active high, rising edge)

I set both buffers at the same time like this: APP_ERROR_CHECK(nrf_drv_spis_buffers_set(&spis, (uint8_t *)m_tx_buf, strlen(m_tx_buf), m_rx_buf, SPI_RX_BUF_SIZE));

buffer should be in heap: static char m_tx_buf[] = "nrf_test\r\n"; /**< TX buffer. */

We can see the same phenomenon on two different master devices from different manufacturers.

EDIT: corrected stuff removed.

[Matts]

And to elaborate. The first byte in the picture should be 0x6A, next 0x65, 0x73. And to me it seems OK in the scope image. However in the buffer there's 0x35, 0x32 ,0xb9. So there's one extra zero(only in first byte) read and all the content after that is offset by one.