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Sketch: support for MCP4151-103 digital pot

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Added support and autodetection of MCP4151 digital pot.
If MCP4151 is detected then its wiper resolution is halved
to match the MCP4131 wiper resolution.
MCP4151-103 is now a drop in replacement for MCP4131-103.
This commit is contained in:
ole00 2023-05-19 22:59:45 +01:00
parent d3acb78576
commit 86a4ade9f9
2 changed files with 46 additions and 4 deletions
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48
aftb_mcp4131.h
View File

@ -1,4 +1,5 @@
//MCP4131 digital pot - bitbanged control //MCP4131 digital pot (bitbanged control) for Afterburner GAL project.
// * compatible with MCP4151 (resolution of the wiper is halved to match MCP4131)
//set default pins //set default pins
#ifndef POT_CS #ifndef POT_CS
@ -26,19 +27,32 @@
#define ADDR_WIPER1 1 #define ADDR_WIPER1 1
#define ADDR_TCON 4 #define ADDR_TCON 4
#define ADDR_STAT 5 #define ADDR_STAT 5
#define ADDR_INCREMENT 100
#define CMD_READ (0b11 << 10) #define CMD_READ (0b11 << 10)
#define CMD_INCREMENT (0b01 << 2)
#define mcp4131_disableWiper() mcp4131_write(ADDR_TCON, 0b111111101) #define mcp4131_disableWiper() mcp4131_write(ADDR_TCON, 0b111111101)
#define mcp4131_enableWiper() mcp4131_write(ADDR_TCON, 0b111111111) #define mcp4131_enableWiper() mcp4131_write(ADDR_TCON, 0b111111111)
#define mcp4131_read(A) mcp4131_reg((A),0,1) #define mcp4131_read(A) mcp4131_reg((A),0,1)
#define mcp4131_write(A,V) mcp4131_reg((A),(V),0) #define mcp4131_write(A,V) mcp4131_reg((A),(V),0)
static uint8_t mcp4151_detected;
// read or write the mcp4131 register // read or write the mcp4131 register
static uint16_t mcp4131_reg(uint8_t address, uint16_t value, uint8_t read_reg) { static uint16_t mcp4131_reg(uint8_t address, uint16_t value, uint8_t read_reg) {
int8_t i; int8_t i = 15; //16 bit command
uint16_t r = address; uint16_t r = address;
r <<= 12; r <<= 12;
if (mcp4151_detected && address == ADDR_WIPER) {
value <<= 1; //multiply the wiper value by 2
}
if (address == ADDR_INCREMENT) {
r = CMD_INCREMENT;
i = 7; // 8 bit command
} else
if (read_reg) { if (read_reg) {
r |= CMD_READ; r |= CMD_READ;
} else { } else {
@ -52,7 +66,6 @@ static uint16_t mcp4131_reg(uint8_t address, uint16_t value, uint8_t read_reg)
//activate IC //activate IC
digitalWrite(POT_CS, 0); digitalWrite(POT_CS, 0);
i = 15;
while (i >= 0) { while (i >= 0) {
//write address and command (bits 15 to 10) //write address and command (bits 15 to 10)
if ((!read_reg) || i > 9) { if ((!read_reg) || i > 9) {
@ -78,6 +91,10 @@ static uint16_t mcp4131_reg(uint8_t address, uint16_t value, uint8_t read_reg)
pinMode(POT_DAT, OUTPUT); pinMode(POT_DAT, OUTPUT);
} }
if (mcp4151_detected && address == ADDR_WIPER && read_reg) {
value >>= 1; //divide the wiper value by 2
}
//disable IC //disable IC
digitalWrite(POT_CS, 1); digitalWrite(POT_CS, 1);
return r & 0x1FF; //clamp value to 9 bits return r & 0x1FF; //clamp value to 9 bits
@ -95,6 +112,9 @@ static void mcp4131_init(void) {
// returns 1 if POT is detected, 0 otherwise // returns 1 if POT is detected, 0 otherwise
static uint8_t mcp4131_detect(void) { static uint8_t mcp4131_detect(void) {
uint16_t r; uint16_t r;
mcp4151_detected = 0;
mcp4131_disableWiper(); mcp4131_disableWiper();
//note checking is done while the wiper is disabled - no resistance is applied //note checking is done while the wiper is disabled - no resistance is applied
@ -108,6 +128,28 @@ static uint8_t mcp4131_detect(void) {
if (r != 0b101) { if (r != 0b101) {
return 0; return 0;
} }
//sanity check whether the incrementing works
mcp4131_write(ADDR_WIPER, 127);
mcp4131_write(ADDR_INCREMENT, 0);
r = mcp4131_read(ADDR_WIPER);
if (r != 128) {
return 0;
}
//detect MCP4151 by incrementing again - MCP4131 clamps the value to 128, MCP4151 increments to 129
mcp4131_write(ADDR_INCREMENT, 0);
r = mcp4131_read(ADDR_WIPER);
#if 0
Serial.print(F("MCP41541 detect: "));
Serial.println(r == 129 ? 1 : 0, DEC);
#endif
if (r == 129) {
mcp4151_detected = 1;
} else
if (r != 128) {
return 0; //error - the value should be clamped to 128
}
mcp4131_write(ADDR_WIPER, POT_DEFAULT_VALUE); mcp4131_write(ADDR_WIPER, POT_DEFAULT_VALUE);
#if POT_WIPER_ENABLED #if POT_WIPER_ENABLED
mcp4131_enableWiper(); mcp4131_enableWiper();

2
afterburner.ino
View File

@ -34,7 +34,7 @@
*/ */
#define VERSION "0.5.0" #define VERSION "0.5.2"
//#define DEBUG_PES //#define DEBUG_PES
//#define DEBUG_VERIFY //#define DEBUG_VERIFY