Datasheet

914
998
CTRL_LANE1_SIGNED controls whether BASE0 and BASE1 are sign-extended for this interpolation (this sign extension is
required because the interpolation produces an intermediate product value 40 bits in size). CTRL_LANE0_SIGNED continues
to control the sign extension of the lane 0 intermediate result in PEEK2, POP2 as normal.
Pico Examples: https://github.com/raspberrypi/pico-examples/tree/master/interp/hello_interp/hello_interp.c Lines 87 - 118
Ê87 void print_simple_blend2_results(bool is_signed) {
Ê88 // lane 1 signed flag controls whether base 0/1 are treated as signed or unsigned
Ê89 interp_config cfg = interp_default_config();
Ê90 interp_config_set_signed(&cfg, is_signed);
Ê91 interp_set_config(interp0, 1, &cfg);
Ê92
Ê93 for (int i = 0; i <= 6; i++) {
Ê94 interp0->accum[1] = 255 * i / 6;
Ê95 if (is_signed) {
Ê96 printf("%d\n", (int) interp0->peek[1]);
Ê97 } else {
Ê98 printf("0x%08x\n", (uint) interp0->peek[1]);
Ê99 }
100 }
101 }
102
103 void simple_blend2() {
104 puts("Simple blend 2:");
105
106 interp_config cfg = interp_default_config();
107 interp_config_set_blend(&cfg, true);
108 interp_set_config(interp0, 0, &cfg);
109
110 interp0->base[0] = -1000;
111 interp0->base[1] = 1000;
112
113 puts("signed:");
114 print_simple_blend2_results(true);
115
116 puts("unsigned:");
117 print_simple_blend2_results(false);
118 }
This should print:
signed:
-1000
-672
-336
-8
328
656
992
unsigned:
0xfffffc18
0xd5fffd60
0xaafffeb0
0x80fffff8
0x56000148
0x2c000290
RP2040 Datasheet
2.3. Processor subsystem 37