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Shorten dshot pulse width #20379

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merged 2 commits into from
Mar 30, 2022
+36 −19
Merged

Shorten dshot pulse width #20379

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d079a46
AP_HAL: update prescaler tests
andyp1per Mar 8, 2022
e0c0f4e
AP_HAL_ChibiOS: use narrower bitwidths for dshot and LEDs to allow mo…
andyp1per Mar 8, 2022
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14 changes: 7 additions & 7 deletions libraries/AP_HAL/tests/test_prescaler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,36 +11,36 @@ class PrescalerParameterizedTestFixture :public ::testing::TestWithParam<uint32_
const uint32_t prescaler = AP_HAL::RCOutput::calculate_bitrate_prescaler(clock, target_rate, is_dshot);
// we would like at most a 1% discrepancy in target versus actual
const float rate_delta = fabsf(float(clock / prescaler) - target_rate) / target_rate;
EXPECT_TRUE(rate_delta < 0.20f);
EXPECT_TRUE(rate_delta < 0.13f);
}
};

TEST_P(PrescalerParameterizedTestFixture, DShot150) {
test_prescaler(GetParam(), 150000 * 20, true);
test_prescaler(GetParam(), 150000 * 8, true);
}

TEST_P(PrescalerParameterizedTestFixture, DShot300) {
test_prescaler(GetParam(), 300000 * 20, true);
test_prescaler(GetParam(), 300000 * 8, true);
}

TEST_P(PrescalerParameterizedTestFixture, DShot600) {
test_prescaler(GetParam(), 600000 * 20, true);
test_prescaler(GetParam(), 600000 * 8, true);
}

TEST_P(PrescalerParameterizedTestFixture, DShot1200) {
test_prescaler(GetParam(), 1200000 * 20, true);
test_prescaler(GetParam(), 1200000 * 8, true);
}

TEST_P(PrescalerParameterizedTestFixture, Passthrough) {
test_prescaler(GetParam(), 19200 * 10, false);
}

TEST_P(PrescalerParameterizedTestFixture, NeoPixel) {
test_prescaler(GetParam(), 800000 * 20, false);
test_prescaler(GetParam(), 800000 * 11, false);
}

TEST_P(PrescalerParameterizedTestFixture, ProfiLED) {
test_prescaler(GetParam(), 1500000 * 20, false);
test_prescaler(GetParam(), 1500000 * 11, false);
}

INSTANTIATE_TEST_CASE_P(
Expand Down
41 changes: 29 additions & 12 deletions libraries/AP_HAL_ChibiOS/RCOutput.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,18 @@ static const eventmask_t EVT_PWM_SYNTHETIC_SEND = EVENT_MASK(13);
static const eventmask_t EVT_PWM_SEND_NEXT = EVENT_MASK(14);
static const eventmask_t EVT_LED_SEND = EVENT_MASK(15);

static const uint32_t DSHOT_BIT_WIDTH_TICKS = 8;
static const uint32_t DSHOT_BIT_0_TICKS = 3;
static const uint32_t DSHOT_BIT_1_TICKS = 6;

// See WS2812B spec for expected pulse widths
static const uint32_t NEOP_BIT_WIDTH_TICKS = 11;
static const uint32_t NEOP_BIT_0_TICKS = 4;
static const uint32_t NEOP_BIT_1_TICKS = 9;
// neopixel does not use pulse widths at all
static const uint32_t PROFI_BIT_0_TICKS = 4;
static const uint32_t PROFI_BIT_1_TICKS = 9;

// #pragma GCC optimize("Og")

/*
Expand Down Expand Up @@ -882,7 +894,6 @@ void RCOutput::set_group_mode(pwm_group &group)
}

const uint32_t rate = protocol_bitrate(group.current_mode);
const uint32_t bit_period = 20;

// configure timer driver for DMAR at requested rate
const uint8_t pad_end_bits = 8;
Expand All @@ -893,7 +904,7 @@ void RCOutput::set_group_mode(pwm_group &group)
// calculate min time between pulses taking into account the DMAR parallelism
const uint32_t pulse_time_us = 1000000UL * bit_length / rate;

if (!setup_group_DMA(group, rate, bit_period, active_high, buffer_length, pulse_time_us, false)) {
if (!setup_group_DMA(group, rate, NEOP_BIT_WIDTH_TICKS, active_high, buffer_length, pulse_time_us, false)) {
group.current_mode = MODE_PWM_NONE;
break;
}
Expand All @@ -902,13 +913,12 @@ void RCOutput::set_group_mode(pwm_group &group)

case MODE_PWM_DSHOT150 ... MODE_PWM_DSHOT1200: {
const uint32_t rate = protocol_bitrate(group.current_mode);
const uint32_t bit_period = 20;
bool active_high = is_bidir_dshot_enabled() ? false : true;
// calculate min time between pulses
const uint32_t pulse_send_time_us = 1000000UL * dshot_bit_length / rate;

// configure timer driver for DMAR at requested rate
if (!setup_group_DMA(group, rate, bit_period, active_high,
if (!setup_group_DMA(group, rate, DSHOT_BIT_WIDTH_TICKS, active_high,
MAX(DSHOT_BUFFER_LENGTH, GCR_TELEMETRY_BUFFER_LEN), pulse_send_time_us, true)) {
group.current_mode = MODE_PWM_NORMAL;
break;
Expand Down Expand Up @@ -1293,8 +1303,8 @@ uint16_t RCOutput::create_dshot_packet(const uint16_t value, bool telem_request,
*/
void RCOutput::fill_DMA_buffer_dshot(uint32_t *buffer, uint8_t stride, uint16_t packet, uint16_t clockmul)
{
const uint32_t DSHOT_MOTOR_BIT_0 = 7 * clockmul;
const uint32_t DSHOT_MOTOR_BIT_1 = 14 * clockmul;
const uint32_t DSHOT_MOTOR_BIT_0 = DSHOT_BIT_0_TICKS * clockmul;
const uint32_t DSHOT_MOTOR_BIT_1 = DSHOT_BIT_1_TICKS * clockmul;
uint16_t i = 0;
for (; i < dshot_pre; i++) {
buffer[i * stride] = 0;
Expand Down Expand Up @@ -2181,8 +2191,8 @@ void RCOutput::_set_neopixel_rgb_data(pwm_group *grp, uint8_t idx, uint8_t led,
const uint8_t stride = 4;
uint32_t *buf = grp->dma_buffer + (led * neopixel_bit_length + pad_start_bits) * stride + idx;
uint32_t bits = (green<<16) | (red<<8) | blue;
const uint32_t BIT_0 = 7 * grp->bit_width_mul;
const uint32_t BIT_1 = 14 * grp->bit_width_mul;
const uint32_t BIT_0 = NEOP_BIT_0_TICKS * grp->bit_width_mul;
const uint32_t BIT_1 = NEOP_BIT_1_TICKS * grp->bit_width_mul;
for (uint16_t b=0; b < 24; b++) {
buf[b * stride] = (bits & 0x800000) ? BIT_1 : BIT_0;
bits <<= 1;
Expand All @@ -2200,7 +2210,7 @@ void RCOutput::_set_profiled_rgb_data(pwm_group *grp, uint8_t idx, uint8_t led,
const uint8_t stride = 4;
uint32_t *buf = grp->dma_buffer + (led * bit_length + pad_start_bits) * stride + idx;
uint32_t bits = 0x1000000 | (blue<<16) | (red<<8) | green;
const uint32_t BIT_1 = 14 * grp->bit_width_mul;
const uint32_t BIT_1 = PROFI_BIT_1_TICKS * grp->bit_width_mul;
for (uint16_t b=0; b < bit_length; b++) {
buf[b * stride] = (bits & 0x1000000) ? 0 : BIT_1;
bits <<= 1;
Expand All @@ -2217,7 +2227,7 @@ void RCOutput::_set_profiled_blank_frame(pwm_group *grp, uint8_t idx, uint8_t le
const uint8_t bit_length = 25;
const uint8_t stride = 4;
uint32_t *buf = grp->dma_buffer + (led * bit_length + pad_start_bits) * stride + idx;
const uint32_t BIT_1 = 14 * grp->bit_width_mul;
const uint32_t BIT_1 = PROFI_BIT_1_TICKS * grp->bit_width_mul;
for (uint16_t b=0; b < bit_length; b++) {
buf[b * stride] = BIT_1;
}
Expand All @@ -2232,7 +2242,7 @@ void RCOutput::_set_profiled_clock(pwm_group *grp, uint8_t idx, uint8_t led)
const uint8_t bit_length = 25;
const uint8_t stride = 4;
uint32_t *buf = grp->dma_buffer + (led * bit_length + pad_start_bits) * stride + idx;
const uint32_t BIT_1 = 7 * grp->bit_width_mul;
const uint32_t BIT_1 = PROFI_BIT_0_TICKS * grp->bit_width_mul;
for (uint16_t b=0; b < bit_length; b++) {
buf[b * stride] = BIT_1;
}
Expand Down Expand Up @@ -2370,7 +2380,14 @@ void RCOutput::timer_info(ExpandingString &str)
str.printf("TIMERV1\n");

for (auto &group : pwm_group_list) {
const uint32_t target_freq = &group == serial_group ? 19200 * 10 : protocol_bitrate(group.current_mode) * 20;
uint32_t target_freq;
if (&group == serial_group) {
target_freq = 19200 * 10;
} else if (is_dshot_protocol(group.current_mode)) {
target_freq = protocol_bitrate(group.current_mode) * DSHOT_BIT_WIDTH_TICKS;
} else {
target_freq = protocol_bitrate(group.current_mode) * NEOP_BIT_WIDTH_TICKS;
}
const uint32_t prescaler = calculate_bitrate_prescaler(group.pwm_drv->clock, target_freq, is_dshot_protocol(group.current_mode));
str.printf("TIM%-2u CLK=%4uMhz MODE=%5s FREQ=%8u TGT=%8u\n", group.timer_id, unsigned(group.pwm_drv->clock / 1000000),
get_output_mode_string(group.current_mode),
Expand Down