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Compatibility with 24 bit flash pointers on AVR with more than 64KiB of Flash (ATMEGA1280, ATMEGA2560 etc) #113

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Compatibility with 24 bit flash pointers on AVR with more than 64KiB of Flash (ATMEGA1280, ATMEGA2560 etc) #113

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dcdeae5
make it compatible with >64KiB AVR (ATMEGA2560 etc)
josefpavlik Jan 15, 2026
a805af9
speed up on no change
josefpavlik Jan 15, 2026
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87 changes: 39 additions & 48 deletions Encoder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -106,6 +106,7 @@ class Encoder
interrupts_in_use = attach_interrupt(pin1, &encoder);
interrupts_in_use += attach_interrupt(pin2, &encoder);
#endif
RESET_RAMPZ();
//update_finishup(); // to force linker to include the code (does not work)
}

Expand Down Expand Up @@ -219,6 +220,13 @@ class Encoder
static void update(Encoder_internal_state_t *arg) {
#endif
#if defined(__AVR__)
static const int8_t inctable[16]= //0 - no movement, bit 0 is direction, bits 2 and 1 are the absolute value
{
0, 2, 3, 4, // 0, 1, -1, +2
3, 0, 5, 2, // -1, 0, -2, +1
2, 5, 0, 3, // +1, -2, 0, -1
4, 3, 2, 0 // +2, -1, +1, 0
};
// The compiler believes this is just 1 line of code, so
// it will inline this function into each interrupt
// handler. That's a tiny bit faster, but grows the code.
Expand All @@ -243,65 +251,48 @@ class Encoder
"L%=1:" "and r25, r31" "\n\t"
"breq L%=2" "\n\t" // if (pin2)
"ori r22, 8" "\n\t" // state |= 8
"L%=2:" "ldi r30, lo8(pm(L%=table))" "\n\t"
"ldi r31, hi8(pm(L%=table))" "\n\t"
"L%=2:"
"mov r31, r22" "\n\t" // r31 and r22 = state
"lsr r31" "\n\t"
"lsr r31" "\n\t" // r31 = state >> 2
"st X+, r31" "\n\t" // store new state

"ldi r30, lo8(%1)" "\n\t"
"ldi r31, hi8(%1)" "\n\t"
"add r30, r22" "\n\t"
"adc r31, __zero_reg__" "\n\t"
"asr r22" "\n\t"
"asr r22" "\n\t"
"st X+, r22" "\n\t" // store new state
"ld r22, X+" "\n\t"
"adc r31, __zero_reg__" "\n\t"
"ld r31, Z" "\n\t" // r31 = inctable[state]
"clc" "\n\t"
"ror r31" "\n\t" // direction bit to carry
"breq L%=end" "\n\t" // speed up on no change

"ld r22, X+" "\n\t" // load position to r22:r23:r24:r25
"ld r23, X+" "\n\t"
"ld r24, X+" "\n\t"
"ld r25, X+" "\n\t"
"ijmp" "\n\t" // jumps to update_finishup()
// TODO move this table to another static function,
// so it doesn't get needlessly duplicated. Easier
// said than done, due to linker issues and inlining
"L%=table:" "\n\t"
"rjmp L%=end" "\n\t" // 0
"rjmp L%=plus1" "\n\t" // 1
"rjmp L%=minus1" "\n\t" // 2
"rjmp L%=plus2" "\n\t" // 3
"rjmp L%=minus1" "\n\t" // 4
"rjmp L%=end" "\n\t" // 5
"rjmp L%=minus2" "\n\t" // 6
"rjmp L%=plus1" "\n\t" // 7
"rjmp L%=plus1" "\n\t" // 8
"rjmp L%=minus2" "\n\t" // 9
"rjmp L%=end" "\n\t" // 10
"rjmp L%=minus1" "\n\t" // 11
"rjmp L%=plus2" "\n\t" // 12
"rjmp L%=minus1" "\n\t" // 13
"rjmp L%=plus1" "\n\t" // 14
"rjmp L%=end" "\n\t" // 15
"L%=minus2:" "\n\t"
"subi r22, 2" "\n\t"
"sbci r23, 0" "\n\t"
"sbci r24, 0" "\n\t"
"sbci r25, 0" "\n\t"
"rjmp L%=store" "\n\t"
"L%=minus1:" "\n\t"
"subi r22, 1" "\n\t"
"sbci r23, 0" "\n\t"
"sbci r24, 0" "\n\t"
"sbci r25, 0" "\n\t"

"brcs L%=minus" "\n\t"
// position plus r31
"add r22, r31" "\n\t" "\n\t"
"adc r23, __zero_reg__" "\n\t"
"adc r24, __zero_reg__" "\n\t"
"adc r25, __zero_reg__" "\n\t"
"rjmp L%=store" "\n\t"
"L%=plus2:" "\n\t"
"subi r22, 254" "\n\t"
"rjmp L%=z" "\n\t"
"L%=plus1:" "\n\t"
"subi r22, 255" "\n\t"
"L%=z:" "sbci r23, 255" "\n\t"
"sbci r24, 255" "\n\t"
"sbci r25, 255" "\n\t"
"L%=minus:" "\n\t"
// position minus r31
"sub r22, r31" "\n\t"
"sbc r23, __zero_reg__" "\n\t"
"sbc r24, __zero_reg__" "\n\t"
"sbc r25, __zero_reg__" "\n\t"
"L%=store:" "\n\t"
"st -X, r25" "\n\t"
"st -X, r24" "\n\t"
"st -X, r23" "\n\t"
"st -X, r22" "\n\t"
"L%=end:" "\n"
: : "x" (arg) : "r22", "r23", "r24", "r25", "r30", "r31");
:
: "x" (arg), "i"(inctable)
: "r22", "r23", "r24", "r25", "r30", "r31");
#else
uint8_t p1val = DIRECT_PIN_READ(arg->pin1_register, arg->pin1_bitmask);
uint8_t p2val = DIRECT_PIN_READ(arg->pin2_register, arg->pin2_bitmask);
Expand Down
22 changes: 21 additions & 1 deletion utility/direct_pin_read.h
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Original file line number Diff line number Diff line change
@@ -1,8 +1,28 @@
#ifndef direct_pin_read_h_
#define direct_pin_read_h_

#if defined(__AVR__)
#if defined(RAMPZ)
#define RESET_RAMPZ() do {RAMPZ = 0;} while (0)
#else
#define RESET_RAMPZ() do {} while (0)
#endif


#if defined(__AVR__) && defined(RAMPZ)

#define portInputRegister_far(P) ( (volatile uint8_t *)( pgm_read_word_far( pgm_get_far_address(port_to_input_PGM) + 2*(P))) )
#define digitalPinToBitMask_far(P) ( pgm_read_byte_far( pgm_get_far_address(digital_pin_to_bit_mask_PGM) + (P) ) )
#define digitalPinToPort_far(P) ( pgm_read_byte_far( pgm_get_far_address(digital_pin_to_port_PGM) + (P) ) )


#define IO_REG_TYPE uint8_t
#define PIN_TO_BASEREG(pin) (portInputRegister_far(digitalPinToPort_far(pin)))
#define PIN_TO_BITMASK(pin) (digitalPinToBitMask_far(pin))
#define DIRECT_PIN_READ(base, mask) (((*(base)) & (mask)) ? 1 : 0)

#elif defined(__AVR__)

#define IO_REG_TYPE uint8_t
#define PIN_TO_BASEREG(pin) (portInputRegister(digitalPinToPort(pin)))
#define PIN_TO_BITMASK(pin) (digitalPinToBitMask(pin))
#define DIRECT_PIN_READ(base, mask) (((*(base)) & (mask)) ? 1 : 0)
Expand Down