Jimmy Hack / MAX500

The MAX500 is an 8 bit DAC that can output to higher voltages (~12V). The chip has 4 onboard DAC channels.

Dependencies:   DAC

MAX500.cpp@1:90b59ae53d25, 2013-07-16 (annotated)

Committer:
JimmyTheHack
Date:
Tue Jul 16 06:06:21 2013 +0000
Revision:
1:90b59ae53d25
Parent:
0:b74d88185698 
attempt at making DAC_SPI libraries separate

Who changed what in which revision?

UserRevisionLine numberNew contents of line
JimmyTheHack 0:b74d88185698 1 #include "MAX500.h"
JimmyTheHack 0:b74d88185698 2
JimmyTheHack 0:b74d88185698 3 MAX500::MAX500(int SPIchannelNum, PinName _LOAD, PinName _LDAC) : DAC_SPI(SPIchannelNum, _LOAD, _LDAC){ //We use the 3 wire serial interface, since the timing is more standardized.
JimmyTheHack 0:b74d88185698 4 (*DACspi).format(10,2); //messages use a 10 bit word, and read data on the falling edge with the clock defaulting to HIGH.
JimmyTheHack 0:b74d88185698 5 frequency(5000000); //set default frequency to 5MHz since unstated
JimmyTheHack 0:b74d88185698 6 autoUpdate=1;
JimmyTheHack 0:b74d88185698 7 VrefAB=5000; //assume a 5V reference voltage for use with write_mv(). This value can be configured;
JimmyTheHack 0:b74d88185698 8 VrefC=5000; //assume a 5V reference voltage for use with write_mv(). This value can be configured;
JimmyTheHack 0:b74d88185698 9 VrefD=5000; //assume a 5V reference voltage for use with write_mv(). This value can be configured;
JimmyTheHack 0:b74d88185698 10 CS=1; //CS is our LOAD pin
JimmyTheHack 0:b74d88185698 11 }
JimmyTheHack 0:b74d88185698 12
JimmyTheHack 0:b74d88185698 13 void MAX500::select(char DACnum){
JimmyTheHack 0:b74d88185698 14 DACselect=DACnum & 0x03; //choose between DAC A , B, C or D
JimmyTheHack 0:b74d88185698 15 }
JimmyTheHack 0:b74d88185698 16
JimmyTheHack 0:b74d88185698 17 void MAX500::write_mV(int mV){
JimmyTheHack 0:b74d88185698 18 int Vref;
JimmyTheHack 0:b74d88185698 19 if (DACselect==0 || DACselect ==1){
JimmyTheHack 0:b74d88185698 20 Vref=VrefAB;
JimmyTheHack 0:b74d88185698 21 }
JimmyTheHack 0:b74d88185698 22 else if (DACselect ==2) {
JimmyTheHack 0:b74d88185698 23 Vref=VrefC;
JimmyTheHack 0:b74d88185698 24 }
JimmyTheHack 0:b74d88185698 25 else{
JimmyTheHack 0:b74d88185698 26 Vref=VrefD;
JimmyTheHack 0:b74d88185698 27 }
JimmyTheHack 0:b74d88185698 28 int DACvalue= mV* 255/Vref ; //scale voltage to a DAC value.
JimmyTheHack 0:b74d88185698 29 write(DACvalue);
JimmyTheHack 0:b74d88185698 30 }
JimmyTheHack 0:b74d88185698 31
JimmyTheHack 0:b74d88185698 32 void MAX500::write(int value){
JimmyTheHack 0:b74d88185698 33 //valid input values are 0 - 255. 255 should scale to Vref.
JimmyTheHack 0:b74d88185698 34 //All serial commands are 10 bit words. The highest 2 bits are control bits, while the last 8 are the data bits for the 8-bit DAC MAX500.
JimmyTheHack 0:b74d88185698 35
JimmyTheHack 0:b74d88185698 36 //bit 9-8: Selection bits for DAC
JimmyTheHack 0:b74d88185698 37 //bit 7-0: Data bits for the DAC.
JimmyTheHack 0:b74d88185698 38
JimmyTheHack 0:b74d88185698 39 if (value > 0x0FF){
JimmyTheHack 0:b74d88185698 40 value = 0x0FF; //any out of range values will be truncated to our max value
JimmyTheHack 0:b74d88185698 41 }
JimmyTheHack 0:b74d88185698 42 value=value & 0x0FF; //limit our value to 8 bits.
JimmyTheHack 0:b74d88185698 43
JimmyTheHack 0:b74d88185698 44 //SCK=0; //set the clock low.
JimmyTheHack 0:b74d88185698 45 LDAC=1;
JimmyTheHack 0:b74d88185698 46 CS=1; //enable the chip to recieve data
JimmyTheHack 0:b74d88185698 47
JimmyTheHack 0:b74d88185698 48 int message= (DACselect<<8)+value;
JimmyTheHack 0:b74d88185698 49 (*DACspi).write(message);
JimmyTheHack 0:b74d88185698 50 //wait_us(5);
JimmyTheHack 0:b74d88185698 51 CS=0; //signal end of message. The data will be loaded into the internal registers.
JimmyTheHack 0:b74d88185698 52 //wait_us(5);
JimmyTheHack 0:b74d88185698 53 CS=1;
JimmyTheHack 0:b74d88185698 54 if(autoUpdate){ LDAC=0;} //trigger the update of the output voltage.
JimmyTheHack 0:b74d88185698 55
JimmyTheHack 0:b74d88185698 56 }
JimmyTheHack 0:b74d88185698 57 void MAX500::update(){
JimmyTheHack 0:b74d88185698 58 //triggers the DAC to update output on command. Useful if we wish to synchronize the DAC output value with another event.
JimmyTheHack 0:b74d88185698 59 LDAC=0;
JimmyTheHack 0:b74d88185698 60 }
JimmyTheHack 0:b74d88185698 61