josheeg
Member
SPI Loopback on maple is what I am looking to setup.
The SPI port is the next part of maple software I want to run the ads1298 biopotential mesurement chip by TI.
Can I setup first SPI port 1 then SPI port 2 one master one slave and get the correct setup for 24 or 32 bits being sent out of the maple.
The output I think is 2 bytes 1 for command 1 for the data.
http://leaflabs.com/docs/maple/spi/
is where I am looking.
What vareables do I write to etc.?
josheeg
Member
Here is the code I have so far but what to write and read from when it comes to vareables what registers to check etc.? I assume the registers are different than the arduino.
//hello world with a SPI loop back twistvoid setup() {
HardwareSPI Spi(1);
Spi.begin(SPI_140_625KHZ , MSBFIRST, 0);}
void loop() {
SerialUSB.println("Hello World!");
}
josheeg
Member
I think the arduino spi program requires or uses interupts.
"External interrupts (attachInterrupt()/detachInterrupt()) are implemented (see the external interrupts reference page for more information). " the latest blog posts show this.
Polling the DRDY pin and polling the SPI port could work especaly if it keeps the code easier to fallow.
josheeg
Member
I am getting a error:
error: 'SPI' was not declared in this scope
Here is the example I am trying to wire together from the documentation.
//hello world with a SPI loop back twist
char n=255;
void setup() {
HardwareSPI Spi(1);
Spi.begin(SPI_140_625KHZ , MSBFIRST, 0);}
void loop() {
SerialUSB.println("Hello World!");n = Spi.transfer(0x2A); // sends the byte 0x2A
// and returns the byte receivedn = Spi.transfer(0x2A, 2); // waits 2 usec, then sends the byte 0x2A
// and returns the byte received}
josheeg
Member
I tried the same code as above using Spi.send(data, size()
as shown on the leaflabs website.
`</p>
<p>//hello world with a SPI loop back twist</p>
<p>char n=255;</p>
<p>void setup() {<br />
HardwareSPI Spi(1);<br />
Spi.begin(SPI_140_625KHZ , MSBFIRST, 0);</p>
<p>}</p>
<p>void loop() {<br />
SerialUSB.println("Hello World!");</p>
<p>Spi.send(n, size(n));</p>
<p>}</p>
<p>`
How does this function return characters? the other spi program
n=spi.....
that returns something when it writes something.
For use of SPI, you need to run port 1 faster than the minimum speed.
An example of using SPI can be found here:
http://www.crennsmind.com/Code/Maple/SPI/ADXL345-Code_Current_SPI1.txt
EDIT: Also note the SPI library only supports Master mode.
josheeg
Member
I do not know where documentation says what you said how would I do that?
For use of SPI, you need to run port 1 faster than the minimum speed.
So I could not create a loopback? on the same port miso to mosi?
I agree it seems the maple seems to only be able to be master.
It looks like after me trying to get the code to work it reads when it writes.
but also it requires uint8 data types that are not colored. I like them better because I know what size data I am working with at least.
The code seems to return one byte and send a array so I would send a array with 1 element to get one thing back? Also it seems to want a array of uint8 's but wants it in the format of " o=Spi.send(&n[0], temp);"
The & sign confuses me so it gets the address of the array element zero so would return one character?
//hello world with a SPI loop back twist//this has to be added at the top above setup
HardwareSPI Spi(1);uint8 n[1];
uint32 temp=0;
uint8 o=0;void setup() {
Spi.begin(SPI_140_625KHZ , MSBFIRST, 0);
n[0]=255;
n[1]=1;
}void loop() {
SerialUSB.println("Hello World!");temp=sizeof(n);
o=Spi.send(&n[0], temp);
}
The documentation doesn't mention it, but the library does! You can either uses SPI port 2 or change:
Spi.begin(SPI_140_625KHZ , MSBFIRST, 0);
to
Spi.begin(SPI_281_250KHZ , MSBFIRST, 0);
You can create a loop back purely by just connecting MOSI to MISO.
Slave SPI is possible with the Maple, however it requires a manual setup.
You can just use:
o=Spi.send(n, temp);
But as you might know, it only returns the last byte, however, if you send each byte separate, you can get each byte back. It's also possible to modify the library, however I'll leave that for the LeafLabs team if they wish to do that.
josheeg
Member
SPI_281_250KHZ added in compiles but at a lower frequency. So your saying SPI port 1 is less than the max speed of port 2. Also this is not in the maple documentation?
A loop back is done "by just connecting MOSI to MISO." Ok got that.
So to get eatch byte send indivigual bytes.
Otherwise if I use a array it will send a series of bytes starting at n[0] to n[N]
returning the last thing back on the SPI port.
This does not compile:
You can just use:
o=Spi.send(n, temp);
This does I need a &n for some reason it wants &n should I initilise it differently or use n differently? &n[0] also works should that be the begining or the end of the string I should pass in?
temp=sizeof(n);
o=Spi.send(&n, temp);
josheeg
Member
Oh I was working with port 1 the whole time so port 2 I would have to define in the begining but don't think I can work with both that is proably why it would compile for eather.
n 1 unit8 spaces? well both point first to a arrays pointer or something you have to put a & infront of it was what I was saying. temp was just something I used to store the size of the array but said to be a 32 bit pointer.
I didn't try any code I just compiled it.
n 1 unit8 spaces? well both point first to a arrays pointer or something you have to put a & infront of it was what I was saying. temp was just something I used to store the size of the array but said to be a 32 bit pointer.
As in when you declared the array.
uint8 n[1];
compared to:
uint8 n[2];
Oh I was working with port 1 the whole time so port 2 I would have to define in the begining but don't think I can work with both that is proably why it would compile for eather.
You can use both, they're both hardware implementations of SPI.
Crenn:
Slave SPI is possible with the Maple, however it requires a manual setup.
I have been trying to do this but I'm new to the Cortex family of processors. Do you by chance have an example of how to do this?
TIA,
Dustin
josheeg
Member
Well DeamonMaker does your other device create the clock signal? If so then it is the master that is what that means in SPI. If that is the case the slave does something when the clock is triggered useualy shift data in or out. So that could be a hardware spi read that is also a write.
http://arduino.cc/en/Reference/ShiftOut
shiftout might be useful
otherwise it is a read in.
The clock pin could be considered something you would want to interupt your maples program on they just came out with interupts for the arduino like maple language.
External interrupts (attachInterrupt()/detachInterrupt()) are implemented (see the external interrupts reference page for more information).
they can act and react on rising or falling or changing clock, that sounds like spi.
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