spi read from an arduino program

[cobra1]

Hi.

Could this be converted to a flowcode chart??

uchar Read_MFRC522(uchar addr)

{uchar val;digitalWrite(chipSelectPin, LOW);

//address format：1XXXXXX0
SPI.transfer(((addr<<1)&0x7E) | 0x80);
val =SPI.transfer(0x00);

digitalWrite(chipSelectPin, HIGH);

return val;

I dont understand where return val is pulled from????

[Benj]

Hello,

Yes this looks fairly simple to achieve. Which version of Flowcode are you wanting to use?

[cobra1]

Im using version 3.

[cobra1]

Do you understand where the return val variable is being loaded from??

[cobra1]

Hi.

Could this be converted to a flowcode chart??

uchar Read_MFRC522(uchar addr)

{uchar val;digitalWrite(chipSelectPin, LOW);

//address format：1XXXXXX0
SPI.transfer(((addr<<1)&0x7E) | 0x80);
val =SPI.transfer(0x00);

digitalWrite(chipSelectPin, HIGH);

return val;

I dont understand where return val is pulled from????

Im not at a computer so cant test this yet but i wanted to see if this looks right.

CS = Low

addr = 0x14
Spidata = (((addr<<1)&0x7E) | 0x80);
SEND SPI BYTE (Spidata)

RECEIVE SPI BYTE (Val) not sure why the origional has 0x00
Return Val = Val

CS = High


Does this look like it will work??

[Benj]

Hello,

Yep that looks spot on.

RECEIVE SPI BYTE (Val) not sure why the origional has 0x00

A SPI transaction simultaneously transfers and receives a byte at the same time. Generally you only want to be able to read or write at any one time so the Flowcode macros mask off the surplus value to make things more straightforward. In your case the 0x00 is being sent when calling the receive macro but really it could be anything as it is the incoming value you are interested in.

[cobra1]

Thanks for clearing that up ben. Will see if it works when i get home

[cobra1]

I have another question...


How would you deal with this?

WRITE_SPI (Register, Temp | Mask)

and also

WRITE_SPI (Register, Temp & (~Mask))


Mask = 0x80

Temp is a byte read from a read function.


I havnt done masking before so this is a bit new to me.

[dazz]

Hi Cobra
Could you post the arduino code in a code box as it might make it easier to help

Regards
Dazz

[cobra1]

Code: Select all

* Function：SetBitMask
 * Description：set RC522 register bit
 * Input parameter：reg--register address;mask--value
 * Return：null
 */
void SetBitMask(uchar reg, uchar mask)  
{
    uchar tmp;
    tmp = Read_MFRC522(reg);
    Write_MFRC522(reg, tmp | mask);  // set bit mask
}

 
 /*
 * Function：ClearBitMask
 * Description：clear RC522 register bit
 * Input parameter：reg--register address;mask--value
 * Return：null
 */
void ClearBitMask(uchar reg, uchar mask)  
{
    uchar tmp;
    tmp = Read_MFRC522(reg);
    Write_MFRC522(reg, tmp & (~mask));  // clear bit mask
}