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Add RP2040 single-wire UART write path for TMC2209 stepper drivers #319

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Add RP2040 single-wire UART write path for TMC2209 stepper drivers #319

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70 changes: 54 additions & 16 deletions src/source/TMC2208Stepper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,10 @@
#include "TMC_MACROS.h"
#include "SERIAL_SWITCH.h"

#if defined(ARDUINO_ARCH_RP2040) && defined(RP2040_SINGLE_WIRE_UART_PIN)
#include <hardware/gpio.h>
#endif

// Protected
// addr needed for TMC2209
TMC2208Stepper::TMC2208Stepper(Stream * SerialPort, float RS, uint8_t addr) :
Expand Down Expand Up @@ -201,8 +205,41 @@ void TMC2208Stepper::write(uint8_t addr, uint32_t regVal) {
delay(replyDelay);
}

#if defined(ARDUINO_ARCH_RP2040) && defined(RP2040_SINGLE_WIRE_UART_PIN)
#include <hardware/gpio.h>
// Bit-bang one 8N1 UART byte on the single-wire PDN_UART pin.
// Temporarily switches GPIO to SIO output for TX, then restores UART RX mode.
// 9 µs/bit ≈ 111 kbaud (-3.7% vs 115200) — within the ±6.25% 8N1 tolerance.
static void _rp2040_sw_uart_write_byte(uint8_t byte) {
constexpr uint32_t T = 9; // µs per bit
gpio_set_function(RP2040_SINGLE_WIRE_UART_PIN, GPIO_FUNC_SIO);
gpio_set_dir(RP2040_SINGLE_WIRE_UART_PIN, GPIO_OUT);
gpio_put(RP2040_SINGLE_WIRE_UART_PIN, 1); // idle HIGH before start bit
// Start bit
gpio_put(RP2040_SINGLE_WIRE_UART_PIN, 0);
delayMicroseconds(T);
// 8 data bits, LSB first
for (int i = 0; i < 8; i++) {
gpio_put(RP2040_SINGLE_WIRE_UART_PIN, (byte >> i) & 1);
delayMicroseconds(T);
}
// Stop bit
gpio_put(RP2040_SINGLE_WIRE_UART_PIN, 1);
delayMicroseconds(T);
// Restore UART1 RX function on GPIO9
gpio_set_function(RP2040_SINGLE_WIRE_UART_PIN, GPIO_FUNC_UART);
}
#endif

uint64_t TMC2208Stepper::_sendDatagram(uint8_t datagram[], const uint8_t len, uint16_t timeout) {
while (available() > 0) serial_read(); // Flush
// === STEP 0: flush stale RX bytes ===
{
uint32_t _flush_t0 = micros();
while (available() > 0) {
serial_read();
if ((micros() - _flush_t0) > (uint32_t)timeout * 1000UL) break;
}
}

#if defined(ARDUINO_ARCH_AVR)
if (RXTX_pin > 0) {
Expand All @@ -211,29 +248,33 @@ uint64_t TMC2208Stepper::_sendDatagram(uint8_t datagram[], const uint8_t len, ui
}
#endif

// === STEP 1: write request ===
#if defined(ARDUINO_ARCH_RP2040) && defined(RP2040_SINGLE_WIRE_UART_PIN)
noInterrupts();
for(int i=0; i<=len; i++) _rp2040_sw_uart_write_byte(datagram[i]);
interrupts();
#else
for(int i=0; i<=len; i++) serial_write(datagram[i]);
#endif

#if defined(ARDUINO_ARCH_AVR)
if (RXTX_pin > 0) {
pinMode(RXTX_pin, INPUT_PULLUP);
}
#endif

// === STEP 2: reply delay ===
delay(this->replyDelay);

// scan for the rx frame and read it
uint32_t ms = millis();
// === STEP 3: sync scan with micros() timeout ===
uint32_t _sync_t0 = micros();
uint32_t sync_target = (static_cast<uint32_t>(datagram[0])<<16) | 0xFF00 | datagram[2];
uint32_t sync = 0;

do {
uint32_t ms2 = millis();
if (ms2 != ms) {
// 1ms tick
ms = ms2;
timeout--;
if ((micros() - _sync_t0) > (uint32_t)timeout * 1000UL) {
return 0;
}
if (!timeout) return 0;

int16_t res = serial_read();
if (res < 0) continue;
Expand All @@ -244,18 +285,15 @@ uint64_t TMC2208Stepper::_sendDatagram(uint8_t datagram[], const uint8_t len, ui

} while (sync != sync_target);

// === STEP 4: body read ===
uint64_t out = sync;
ms = millis();
uint32_t _body_t0 = micros();
timeout = this->abort_window;

for(uint8_t i=0; i<5;) {
uint32_t ms2 = millis();
if (ms2 != ms) {
// 1ms tick
ms = ms2;
timeout--;
if ((micros() - _body_t0) > (uint32_t)timeout * 1000UL) {
return 0;
}
if (!timeout) return 0;

int16_t res = serial_read();
if (res < 0) continue;
Expand Down