Thread: tuncated uint8_t

Hi all!

I need to set a SPI which is 159 bits long. This is the code:

Code:

SpiTransfer(FALSE, SPI_SETTING_, F_1KHZ_, Spi_Word, Spi_Readback, DATA_LENGTH_);

And this is the array which keeps the SPI word:

Code:

uint8_t Spi_Word[20]=
{ 
0x00, 0x00, 0x26, 0x05, 0x00,
0x01, 0x68, 0x00, 0x0F, 0x80,
0x00, 0x00, 0x00, 0x00, 0xC1,
0xCF, 0x72, 0xE8, 0x60, 0x20,
};

The problem is that the SPi_Word gets truncated, but I don't know why... Besides I don't know why it gets truncated, I don't know how to solf this issue.

Any help would be appreciated,

Regards,

Coen

Thanks for the reply,

DATA_LENGTH_ is indeed 20.
Instead of sending 0x26 (00100110), it sends 0x4C (01001100).
So the MSB is truncated off.

The function looks like this:

Code:

typedef uint8_t __stdcall SpiTransfer_type(uint8_t LsbFirst, uint8_t SPIMode, uint8_t speed, uint8_t *pwrite, uint8_t *pread, uint16_t len);

extern SpiTransfer_type *SpiTransfer;

And this is the (terrible) description of the function:

- If LsbFirst is true (1), the first bit transfered is the LSB (Bit 0), if it is false (0), the MSB (Bit 7) will be transfered first.
- SPIMode defines the idle state of the clockline and the edges data is transfered:
Bit 0 = 0: The Idle state of SCK is 0. The leading edge is a 0 to 1 transition, trailing edge a 1 to 0 transition
Bit 0 = 1: The Idle state of SCK is 1. The leading edge is a 1 to 0 transition, trailing edge a 0 to 1 transition
Bit 1 = 0: Data is sampled at leading edge of SCK and Setup on the trailing edge
Bit 1 = 1: Data is sampled at trailing edge of SCK and Setup on the leading edge
- Speed selects the bitrate of the bus:
0 = 50 kHz
1 = 25 kHz
2 = 10 kHz
3 = 5 kHz
4 = 2 kHz
5 = 1 kHz
- pWrite is an pointer to the data-block what needs to be send.
- pRead is a pointer to the buffer where the read data can be stored. If you’re not interested in the received data you can set pRead to null.
- Len specifies the count of byte to be transfered.

But it does send out 8 bits, only shifted 1 bit to the left. This causes the MSB to be truncated off, and causes the LSB to be 0.

I've written a testprogram, it shows the data what it should be and what it has send. This is what I get:

Code:

00: Send: 00 Received: 00
01: Send: 00 Received: 00
02: Send: 26 Received: 4c
03: Send: 05 Received: 0a
04: Send: 00 Received: 00
05: Send: 01 Received: 02
06: Send: 68 Received: d0
07: Send: 00 Received: 00
08: Send: 0f Received: 1e
09: Send: 80 Received: 00
10: Send: 00 Received: 00
11: Send: 00 Received: 00
12: Send: 00 Received: 00
13: Send: 00 Received: 00
14: Send: c1 Received: 82
15: Send: cf Received: 9e
16: Send: 72 Received: e4
17: Send: e8 Received: d0
18: Send: 60 Received: c0
19: Send: 20 Received: 03

What do you mean with THAT word? Spi_Word?

Of course, that's what you ment sorry about that... That function is part of an dll, that's why I posted the description of it.

I didn't write the dll, so I don't have access to the function itself. But my code is fine as far as you can see?

Let's hope so, because this hang up is killing me

Either way thank you very much for your help, I really appreciated it!