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| author | Ben Isaacs <75862+ben-xo@users.noreply.github.com> | 2021-08-01 14:35:42 +0300 |
|---|---|---|
| committer | Ben Isaacs <75862+ben-xo@users.noreply.github.com> | 2021-08-01 14:35:42 +0300 |
| commit | 9072e07ce68fa60027909131a251b33d74727fde (patch) | |
| tree | edda032d11bfbfd77dbfb5e9c4f55ee2737febcf | |
| parent | 5cc17b2be88982eb34b1998de22b83fee56d4f07 (diff) | |
Tweak clockless trinket to handle negative advanceBy values (that is, showing pixels in reverse).
| -rw-r--r-- | src/platforms/avr/clockless_trinket.h | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/src/platforms/avr/clockless_trinket.h b/src/platforms/avr/clockless_trinket.h index 2cfbef0d..833a2b43 100644 --- a/src/platforms/avr/clockless_trinket.h +++ b/src/platforms/avr/clockless_trinket.h @@ -241,13 +241,13 @@ protected: #define PRESCALEB4(D) asm __volatile__("brcc L_%=\n\tldi %[scale_base], 0xFF\n\tL_%=:\n\tneg %[" #D "]\n\tCLC" ASM_VARS); // Clamp for prescale, increment data, since we won't ever wrap 65k, this also effectively clears carry for us -#define PSBIDATA4(D) asm __volatile__("brcc L_%=\n\tldi %[scale_base], 0xFF\n\tL_%=:\n\tadd %A[data], %[ADV]\n\tadc %B[data], __zero_reg__\n\t" ASM_VARS); +#define PSBIDATA4(D) asm __volatile__("brcc L_%=\n\tldi %[scale_base], 0xFF\n\tL_%=:\n\tadd %A[data], %A[ADV]\n\tadc %B[data], %B[ADV]\n\t" ASM_VARS); #else #define PRESCALE4(D) _dc<4>(loopvar); #define PRESCALEA2(D) _dc<2>(loopvar); #define PRESCALEB4(D) _dc<4>(loopvar); -#define PSBIDATA4(D) asm __volatile__( "add %A[data], %[ADV]\n\tadc %B[data], __zero_reg__\n\trjmp .+0\n\t" ASM_VARS ); +#define PSBIDATA4(D) asm __volatile__( "add %A[data], %A[ADV]\n\tadc %B[data], %B[ADV]\n\trjmp .+0\n\t" ASM_VARS ); #endif // 2 cycles - perform one step of the scaling (if a given bit is set in scale, add scale-base to the scratch space) @@ -299,8 +299,8 @@ protected: #define DONE asm __volatile__("2:" ASM_VARS ); // 2 cycles - increment the data pointer -#define IDATA2 asm __volatile__("add %A[data], %[ADV]\n\tadc %B[data], __zero_reg__\n\t" ASM_VARS ); -#define IDATACLC3 asm __volatile__("add %A[data], %[ADV]\n\tadc %B[data], __zero_reg__\n\t" _CLC1 ASM_VARS ); +#define IDATA2 asm __volatile__("add %A[data], %A[ADV]\n\tadc %B[data], %B[ADV]\n\t" ASM_VARS ); +#define IDATACLC3 asm __volatile__("add %A[data], %A[ADV]\n\tadc %B[data], %B[ADV]\n\t" _CLC1 ASM_VARS ); // 1 cycle mov #define _MOV1(B1, B2) "mov %[" #B1 "], %[" #B2 "]\n\t" @@ -368,7 +368,9 @@ protected: pixels.preStepFirstByteDithering(); // pull the dithering/adjustment values out of the pixels object for direct asm access - uint8_t advanceBy = pixels.advanceBy(); + + // even though advanceBy is only an int8, we cast it to int16 for sign extension in case it's negative. + int16_t advanceBy = pixels.advanceBy(); uint16_t count = pixels.mLen; uint8_t s0 = pixels.mScale.raw[RO(0)]; |