I have the SPI working for full duplex, but for a half-duplex device.
The issue is the *receive* array does not return the correct values.
The O-Scope shows the device is returning the correct values but they are
recorded as the least significant nibble...doubled.
If 0x01 is returned I have 0x03 stored in the array. If 0x0A is returned I
have 0xCC stored in the array. It's as if the "read" only works for the
final 4 bits and at double the speed. Any data in the high nibble is lost.
Has anyone experienced this before or know of something I can do to have
the correct values stored?
This is the code I used.
*int fd, i=0; //file handle and loop counter*
*unsigned char value, null=0x00; //sending only a single char*
*uint8_t bits = 8, mode = 0; //8-bits per word, SPI mode 3*
*uint32_t speed = 4000000; //Speed is 4 MHz (Not Really due
to clock, but it works)*
*unsigned char send_buffer[3];*
*unsigned char receive_buffer[3];*
*int transfer(int fd, unsigned char send[], unsigned char receive[], int
length){*
* struct spi_ioc_transfer transfer[3]; //the transfer structure*
* memset(&transfer, 0, sizeof(transfer));*
* transfer[0].cs_change = 0;*
* transfer[0].tx_buf = (unsigned long) send; //the buffer for sending
data*
* transfer[0].rx_buf = (unsigned long) receive; //the buffer for
receiving data*
* transfer[0].len = length; //the length of buffer*
* transfer[0].speed_hz = speed; //the speed in Hz*
* transfer[0].bits_per_word = bits; //bits per word*
* transfer[0].delay_usecs = 0; //delay in us*
* transfer[0].pad = 0; //delay in us*
* transfer[0].rx_nbits = 8; //delay in us*
* // send the SPI message (all of the above fields, inc. buffers)*
* int status = ioctl(fd, SPI_IOC_MESSAGE(1), &transfer);*
* if (status < 0) {*
* printf("SPI: SPI_IOC_MESSAGE Failed:\t%i", status);*
* return -1;*
* }*
*}*
*int main(){ // The following calls set up the SPI bus properties if
((fd = open(SPI_PATH, O_RDWR))<0){ perror("SPI Error: Can't open
device."); return -1; } if (ioctl(fd, SPI_IOC_WR_MODE,
&mode)==-1){ perror("SPI: Can't set SPI mode."); return -1; }
if (ioctl(fd, SPI_IOC_RD_MODE, &mode)==-1){ perror("SPI: Can't get
SPI mode."); return -1; } if (ioctl(fd, SPI_IOC_WR_BITS_PER_WORD,
&bits)==-1){ perror("SPI: Can't set bits per word."); return -1;
} if (ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits)==-1){ perror("SPI:
Can't get bits per word."); return -1; } if (ioctl(fd,
SPI_IOC_WR_MAX_SPEED_HZ, &speed)==-1){ perror("SPI: Can't set max
speed HZ"); return -1; } if (ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ,
&speed)==-1){ perror("SPI: Can't get max speed HZ."); return -1;
} // Check that the properties have been set printf("SPI Mode is:
%d\n", mode); printf("SPI Bits is: %d\n", bits); printf("SPI Speed is:
%d\n", speed); printf("Attempting to right IDLE to CC1101:\n");
transfer(fd, send_buffer, receive_buffer, 2);}*
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