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swd: use signal as open-drain instead of push-pull, only to make is level shifter compatible

This commit is contained in:
King Kévin 2021-03-22 11:26:35 +01:00
parent 4d64cb35ed
commit 334d8564ff
1 changed files with 8 additions and 3 deletions
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11
lib/swd.c
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@ -177,11 +177,13 @@ bool swd_set_pins(uint32_t swclk_port, uint32_t swclk_pin, uint32_t swdio_port,
rcc_periph_clock_enable(swd_swclk_rcc); // enable clock for GPIO peripheral for clock signal
gpio_set(swd_swclk_port, swd_swclk_pin); // inactive clock is high
gpio_mode_setup(swd_swclk_port, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, swd_swclk_pin); // the host controls the clock
gpio_set_output_options(swd_swclk_port, GPIO_OTYPE_PP, GPIO_OSPEED_50MHZ, swd_swclk_pin); // set SWCLK pin output as push-pull
//gpio_set_output_options(swd_swclk_port, GPIO_OTYPE_PP, GPIO_OSPEED_25MHZ, swd_swclk_pin); // set SWCLK pin output as push-pull
gpio_set_output_options(swd_swclk_port, GPIO_OTYPE_OD, GPIO_OSPEED_25MHZ, swd_swclk_pin); // set SWCLK pin output as open-drain (with external pull-up)
rcc_periph_clock_enable(swd_swdio_rcc); // enable clock for GPIO peripheral for data signal
gpio_set(swd_swdio_port, swd_swdio_pin); // inactive data is high (resetting the target when clock is active)
gpio_mode_setup(swd_swdio_port, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, swd_swdio_pin); // the data signal is half duplex, with the host controlling who is driving the data signal when
gpio_set_output_options(swd_swdio_port, GPIO_OTYPE_PP, GPIO_OSPEED_50MHZ, swd_swdio_pin); // set SWDIO pin output as push-pull
//gpio_set_output_options(swd_swdio_port, GPIO_OTYPE_PP, GPIO_OSPEED_25MHZ, swd_swdio_pin); // set SWDIO pin output as push-pull
gpio_set_output_options(swd_swdio_port, GPIO_OTYPE_OD, GPIO_OSPEED_25MHZ, swd_swdio_pin); // set SWDIO pin output as open-drain (with external pull-up)
return true;
}
@ -203,7 +205,8 @@ uint64_t swd_transaction(uint64_t output, uint8_t bit_count, bool write)
gpio_mode_setup(swd_swdio_port, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, swd_swdio_pin); // we drive the data signal to output data
swd_bits_out = output; // set data to output
} else {
gpio_mode_setup(swd_swdio_port, GPIO_MODE_INPUT, GPIO_PUPD_PULLUP, swd_swdio_pin); // the target will drive the data signal, we just pull it up
//gpio_mode_setup(swd_swdio_port, GPIO_MODE_INPUT, GPIO_PUPD_PULLUP, swd_swdio_pin); // the target will drive the data signal, we just pull it up
gpio_mode_setup(swd_swdio_port, GPIO_MODE_INPUT, GPIO_PUPD_NONE, swd_swdio_pin); // the target will drive the data signal, and there is an external pull-up
swd_bits_out = ~0ULL; // set the value so we pull up
}
swd_bits_in = 0; // reset input buffer
@ -459,7 +462,9 @@ void TIM_ISR(SWD_TIMER)(void)
swd_bits_out &= ~(1ULL << swd_bits_i); // clear bit
}
swd_bits_i++;
gpio_set_output_options(swd_swclk_port, GPIO_OTYPE_PP, GPIO_OSPEED_25MHZ, swd_swclk_pin); // we need an extremely sharp rising edge
gpio_set(swd_swclk_port, swd_swclk_pin); // output rising clock edge
gpio_set_output_options(swd_swclk_port, GPIO_OTYPE_OD, GPIO_OSPEED_25MHZ, swd_swclk_pin); // go back to open-drain once we are high
}
edge_falling = !edge_falling; // remember opposite upcoming edge
} else { // no other interrupt should occur