Hello!
I'm trying to use the PT8211 has a DC DAC with relative success, but my limited coding knowledge is getting me nowhere...
I know the PT8211 is not the best DAC for this application but is understanding is that since the PT8211 is an R-2R ladder DAC this project should be doable for non precision applications, like LFOs etc.
I've tried to modify this code: https://gist.github.com/dilshan/9044b895dcc8aa05d9df0cac1e928f8e
So far i've simply modified the void loop to do a simple Potentiometer follower. But has is, i've stumbled in to some problems:
- i'm having problems to scale the pot value to the full resolution of the DAC, seems like the dac is bias at half the voltage reference and i can only write to one half or the other.
(if i do: int val = map(pot, 0, 4096, 0, 65536); it writes to the top half of the DAC
if i do: int val = map(pot, 0, 4096, 65536, 0); it writes to the bottom half of the DAC)
-can't understand how to select and write to individual DAC channels, the pot value is always updated to both DACs.
Other than this, seems like it works smoothly as a DC DAC and could be a nice/cheap alternative for the more expensive DACs.
What would be needed to modify in order to use it as a simple DC DAC?
Here is where i am so far:
Thanks in advance!
I'm trying to use the PT8211 has a DC DAC with relative success, but my limited coding knowledge is getting me nowhere...
I know the PT8211 is not the best DAC for this application but is understanding is that since the PT8211 is an R-2R ladder DAC this project should be doable for non precision applications, like LFOs etc.
I've tried to modify this code: https://gist.github.com/dilshan/9044b895dcc8aa05d9df0cac1e928f8e
So far i've simply modified the void loop to do a simple Potentiometer follower. But has is, i've stumbled in to some problems:
- i'm having problems to scale the pot value to the full resolution of the DAC, seems like the dac is bias at half the voltage reference and i can only write to one half or the other.
(if i do: int val = map(pot, 0, 4096, 0, 65536); it writes to the top half of the DAC
if i do: int val = map(pot, 0, 4096, 65536, 0); it writes to the bottom half of the DAC)
-can't understand how to select and write to individual DAC channels, the pot value is always updated to both DACs.
Other than this, seems like it works smoothly as a DC DAC and could be a nice/cheap alternative for the more expensive DACs.
What would be needed to modify in order to use it as a simple DC DAC?
Here is where i am so far:
Code:
//#include <limits.h>
#ifndef PIN_BCK
#define PIN_BCK 21
#endif
#ifndef PIN_WS
#define PIN_WS 20
#endif
#ifndef PIN_DIN
#define PIN_DIN 7
#endif
#define NOP __asm__ __volatile__ ("nop\n\t")
void writeDACChannel(short waveData)
{
unsigned char pos = 16;
// Send data into PT8211 in least significant bit justified (LSBJ) format.
while(pos > 0)
{
pos--;
digitalWrite(PIN_BCK, LOW);
// Write next bit in stream into DIN.
digitalWrite(PIN_DIN, (waveData & (1 << pos)) ? HIGH : LOW);
NOP;
// Toggle BCK.
digitalWrite(PIN_BCK, HIGH);
NOP;
}
}
void writeDAC(short waveData)
{
digitalWrite(PIN_WS, LOW);
digitalWrite(PIN_BCK, LOW);
// Write data into right channel of DAC.
writeDACChannel(waveData);
digitalWrite(PIN_WS, HIGH);
// Write data into left channel of DAC.
writeDACChannel(waveData);
}
void setup()
{
pinMode(PIN_BCK, OUTPUT);
pinMode(PIN_WS, OUTPUT);
pinMode(PIN_DIN, OUTPUT);
analogWriteResolution(12);
}
void loop()
{
int pot = analogRead(A0);
int val = map(pot, 0, 4096, 0, 65536);
writeDAC(val);
}Thanks in advance!
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