mirror of
https://github.com/ole00/afterburner.git
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4db4108d4a
New features: * unified socket for 20 pin and 24 devices (including GAL20V8) * variable VPP via digi pot * VPP measurement via A0 ADC (used for VPP calibration)
118 lines
2.8 KiB
C
118 lines
2.8 KiB
C
//MCP4131 digital pot - bitbanged control
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//set default pins
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#ifndef POT_CS
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#define POT_CS A3
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#endif
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#ifndef POT_CLK
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#define POT_CLK A4
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#endif
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#ifndef POT_DAT
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#define POT_DAT A5
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#endif
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#ifndef POT_DEFAULT_VALUE
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#define POT_DEFAULT_VALUE 0x40
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#endif
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#ifndef POT_WIPER_ENABLED
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#define POT_WIPER_ENABLED 0
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#endif
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#define ADDR_WIPER 0
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#define ADDR_WIPER0 0
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#define ADDR_WIPER1 1
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#define ADDR_TCON 4
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#define ADDR_STAT 5
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#define CMD_READ (0b11 << 10)
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#define mcp4131_disableWiper() mcp4131_write(ADDR_TCON, 0b111111101)
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#define mcp4131_enableWiper() mcp4131_write(ADDR_TCON, 0b111111111)
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#define mcp4131_read(A) mcp4131_reg((A),0,1)
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#define mcp4131_write(A,V) mcp4131_reg((A),(V),0)
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// read or write the mcp4131 register
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static uint16_t mcp4131_reg(uint8_t address, uint16_t value, uint8_t read_reg) {
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int8_t i;
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uint16_t r = address;
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r <<= 12;
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if (read_reg) {
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r |= CMD_READ;
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} else {
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r |= value & 0x1FF; // clamp value to 9 bits
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}
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//setup Clock and and Data (SPI mode 0,0)
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digitalWrite(POT_CLK, 0);
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digitalWrite(POT_DAT, 0);
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delayMicroseconds(50);
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//activate IC
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digitalWrite(POT_CS, 0);
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i = 15;
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while (i >= 0) {
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//write address and command (bits 15 to 10)
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if ((!read_reg) || i > 9) {
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uint16_t mask = (1 << i);
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digitalWrite(POT_DAT, (r & mask) ? 1 : 0);
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}
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digitalWrite(POT_CLK, 1); //rise the clock
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//only when reading reg
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if (read_reg) {
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//switch the DAT pin to Input
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if (i == 10) {
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pinMode(POT_DAT, INPUT);
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}
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//read bits 9 to 0
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if (i < 10) {
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r |= (digitalRead(POT_DAT) << i); //read after rising edge
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}
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}
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digitalWrite(POT_CLK, 0); //fall the clock
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i--;
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}
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if (read_reg) {
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pinMode(POT_DAT, OUTPUT);
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}
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//disable IC
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digitalWrite(POT_CS, 1);
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return r & 0x1FF; //clamp value to 9 bits
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}
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static void mcp4131_init(void) {
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pinMode(POT_CS, OUTPUT);
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pinMode(POT_CLK, OUTPUT);
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pinMode(POT_DAT, OUTPUT);
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digitalWrite(POT_CS, 1); //unselect the POT's SPI bus
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}
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// initialisation and detection
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// returns 1 if POT is detected, 0 otherwise
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static uint8_t mcp4131_detect(void) {
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uint16_t r;
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mcp4131_disableWiper();
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//note checking is done while the wiper is disabled - no resistance is applied
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mcp4131_write(ADDR_WIPER, 0b1010);
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r = mcp4131_read(ADDR_WIPER);
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if (r != 0b1010) {
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return 0;
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}
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mcp4131_write(ADDR_WIPER, 0b101);
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r = mcp4131_read(ADDR_WIPER);
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if (r != 0b101) {
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return 0;
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}
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mcp4131_write(ADDR_WIPER, POT_DEFAULT_VALUE);
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#if POT_WIPER_ENABLED
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mcp4131_enableWiper();
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#endif
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return 1;
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}
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