Merge pull request #6328 from KurtE/mixrt_uart_rs485

[mimxrt (teensy) Allow Any GPIO pin for RS485 pin

Author: dhalbert

ports/mimxrt10xx/common-hal/busio/UART.c

@@ -39,6 +39,17 @@
 #include "periph.h"
 
 #include "fsl_lpuart.h"
+#include "fsl_gpio.h"
+// ==========================================================
+// Debug code
+// ==========================================================
+#define ENABLE_DEBUG_PRINTING 0
+#if ENABLE_DEBUG_PRINTING
+#define DBGPrintf mp_printf
+#else
+#define DBGPrintf(p,...)
+#endif
+
 
 // arrays use 0 based numbering: UART1 is stored at index 0
 #define MAX_UART 8
@@ -90,6 +101,7 @@ void common_hal_busio_uart_never_reset(busio_uart_obj_t *self) {
     common_hal_never_reset_pin(self->rx);
     common_hal_never_reset_pin(self->rts);
     common_hal_never_reset_pin(self->cts);
+    common_hal_never_reset_pin(self->rs485_dir);
 }
 
 void common_hal_busio_uart_construct(busio_uart_obj_t *self,
@@ -108,9 +120,12 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
         mp_raise_ValueError(translate("Invalid word/bit length"));
     }
 
+    DBGPrintf(&mp_plat_print, "uart_construct: tx:%p rx:%p rts:%p cts:%p rs485:%p\n", tx, rx, rts, cts, rs485_dir);
+
     // We are transmitting one direction if one pin is NULL and the other isn't.
     bool is_onedirection = (rx == NULL) != (tx == NULL);
     bool uart_taken = false;
+    bool use_rts_for_rs485 = false;
 
     const uint32_t rx_count = MP_ARRAY_SIZE(mcu_uart_rx_list);
     const uint32_t tx_count = MP_ARRAY_SIZE(mcu_uart_tx_list);
@@ -187,11 +202,14 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
 
     // Filter for sane settings for RS485
     if (rs485_dir != NULL) {
+        DBGPrintf(&mp_plat_print, "\t(485 pin): gpio:%p #:%x Mux: %x %x cfg:%x reset:%x %x\n",
+            rs485_dir->gpio, rs485_dir->number, rs485_dir->mux_idx, rs485_dir->mux_reg, rs485_dir->cfg_reg,
+            rs485_dir->mux_reset, rs485_dir->pad_reset);
         if ((rts != NULL) || (cts != NULL)) {
             mp_raise_ValueError(translate("Cannot specify RTS or CTS in RS485 mode"));
         }
-        // For IMXRT the RTS pin is used for RS485 direction
-        rts = rs485_dir;
+        // For IMXRT the RTS pin is used for RS485 direction ???? - Can be will try
+        // it if this is an rts pin.
     } else {
         if (rs485_invert) {
             mp_raise_ValueError(translate("RS485 inversion specified when not in RS485 mode"));
@@ -202,16 +220,22 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     const uint32_t rts_count = MP_ARRAY_SIZE(mcu_uart_rts_list);
     const uint32_t cts_count = MP_ARRAY_SIZE(mcu_uart_cts_list);
 
-    if (rts != NULL) {
+    if ((rts != NULL) || (rs485_dir != NULL)) {
         for (uint32_t i = 0; i < rts_count; ++i) {
             if (mcu_uart_rts_list[i].bank_idx == rx_config->bank_idx) {
                 if (mcu_uart_rts_list[i].pin == rts) {
                     rts_config = &mcu_uart_rts_list[i];
                     break;
+                } else if (mcu_uart_rts_list[i].pin == rs485_dir) {
+                    rts_config = &mcu_uart_rts_list[i];
+                    use_rts_for_rs485 = true;
+                    rts = rs485_dir;
+                    rs485_dir = NULL;
+                    break;
                 }
             }
         }
-        if (rts_config == NULL) {
+        if ((rts != NULL) && (rts_config == NULL)) {
             mp_raise_ValueError_varg(translate("Invalid %q pin"), MP_QSTR_RTS);
         }
     }
@@ -225,7 +249,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
                 }
             }
         }
-        if (cts == NULL) {
+        if (cts_config == NULL) {
             mp_raise_ValueError_varg(translate("Invalid %q pin"), MP_QSTR_CTS);
         }
     }
@@ -257,7 +281,32 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
         config_periph_pin(cts_config);
         self->cts = cts;
     }
+    if (rs485_dir) {
+        DBGPrintf(&mp_plat_print, "\tInit rs485 pin\n");
+        // lets configure this pin as standard GPIO output pin.
+        claim_pin(rs485_dir);
+
+        #define IOMUXC_SW_MUX_CTL_PAD_MUX_MODE_ALT5 5U
+        IOMUXC_SetPinMux(rs485_dir->mux_reg, IOMUXC_SW_MUX_CTL_PAD_MUX_MODE_ALT5, 0, 0, 0, 0);
+        DBGPrintf(&mp_plat_print, "\tAfter IOMUXC_SetPinMux\n");
+        IOMUXC_SetPinConfig(0, 0, 0, 0, rs485_dir->cfg_reg,
+            IOMUXC_SW_PAD_CTL_PAD_HYS(1)
+            | IOMUXC_SW_PAD_CTL_PAD_PUS(0)
+            | IOMUXC_SW_PAD_CTL_PAD_PUE(0)
+            | IOMUXC_SW_PAD_CTL_PAD_PKE(1)
+            | IOMUXC_SW_PAD_CTL_PAD_ODE(0)
+            | IOMUXC_SW_PAD_CTL_PAD_SPEED(2)
+            | IOMUXC_SW_PAD_CTL_PAD_DSE(1)
+            | IOMUXC_SW_PAD_CTL_PAD_SRE(0));
+        DBGPrintf(&mp_plat_print, "\tAfter IOMUXC_SetPinConfig\n");
+
+        const gpio_pin_config_t config = { kGPIO_DigitalOutput, rs485_invert, kGPIO_NoIntmode };
+        GPIO_PinInit(rs485_dir->gpio, rs485_dir->number, &config);
+        DBGPrintf(&mp_plat_print, "\tAfter GPIO_PinInit\n");
+        self->rs485_dir = rs485_dir;
+        self->rs485_invert = rs485_invert;
 
+    }
     lpuart_config_t config = { 0 };
     LPUART_GetDefaultConfig(&config);
 
@@ -279,7 +328,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     // Before we init, setup RS485 direction pin
     // ..unfortunately this isn't done by the driver library
     uint32_t modir = (self->uart->MODIR) & ~(LPUART_MODIR_TXRTSPOL_MASK | LPUART_MODIR_TXRTSE_MASK);
-    if (rs485_dir != NULL) {
+    if (use_rts_for_rs485) {
         modir |= LPUART_MODIR_TXRTSE_MASK;
         if (rs485_invert) {
             modir |= LPUART_MODIR_TXRTSPOL_MASK;
@@ -311,6 +360,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
 
         claim_pin(self->rx);
     }
+    DBGPrintf(&mp_plat_print, "\t<< Init completed >>\n");
 }
 
 bool common_hal_busio_uart_deinited(busio_uart_obj_t *self) {
@@ -330,9 +380,16 @@ void common_hal_busio_uart_deinit(busio_uart_obj_t *self) {
 
     common_hal_reset_pin(self->rx);
     common_hal_reset_pin(self->tx);
+    common_hal_reset_pin(self->cts);
+    common_hal_reset_pin(self->rts);
+    common_hal_reset_pin(self->rs485_dir);
 
     self->rx = NULL;
     self->tx = NULL;
+    self->cts = NULL;
+    self->rts = NULL;
+    self->rs485_dir = NULL;
+
 }
 
 // Read characters.
@@ -371,6 +428,10 @@ size_t common_hal_busio_uart_read(busio_uart_obj_t *self, uint8_t *data, size_t
         uint32_t recvd = 0;
         LPUART_TransferGetReceiveCount(self->uart, &self->handle, &recvd);
         LPUART_TransferAbortReceive(self->uart, &self->handle);
+        if (recvd == 0) {
+            *errcode = EAGAIN;
+            return MP_STREAM_ERROR;
+        }
         return recvd;
     }
 
@@ -393,8 +454,21 @@ size_t common_hal_busio_uart_write(busio_uart_obj_t *self, const uint8_t *data,
     if (self->tx == NULL) {
         mp_raise_ValueError(translate("No TX pin"));
     }
-
-    LPUART_WriteBlocking(self->uart, data, len);
+    if (self->rs485_dir && len) {
+        GPIO_PinWrite(self->rs485_dir->gpio, self->rs485_dir->number, !self->rs485_invert);
+        LPUART_WriteBlocking(self->uart, data, len);
+        // Probably need to verify we have completed output.
+        uint32_t dont_hang_count = 0xffff;
+        while (dont_hang_count--) {
+            if (LPUART_GetStatusFlags(self->uart) & kLPUART_TransmissionCompleteFlag) {
+                break; // hardware says it completed.
+            }
+        }
+        GPIO_PinWrite(self->rs485_dir->gpio, self->rs485_dir->number, self->rs485_invert);
+    } else {
+        // could combine with above but would go through two ifs
+        LPUART_WriteBlocking(self->uart, data, len);
+    }
 
     return len;
 }

ports/mimxrt10xx/common-hal/busio/UART.h

@@ -50,6 +50,9 @@ typedef struct {
     const mcu_pin_obj_t *tx;
     const mcu_pin_obj_t *cts;
     const mcu_pin_obj_t *rts;
+    const mcu_pin_obj_t *rs485_dir;
+    bool rs485_invert;
+
 } busio_uart_obj_t;
 
 void uart_reset(void);

shared-bindings/busio/UART.c

@@ -63,7 +63,12 @@
 //|         :param int receiver_buffer_size: the character length of the read buffer (0 to disable). (When a character is 9 bits the buffer will be 2 * receiver_buffer_size bytes.)
 //|
 //|         *New in CircuitPython 4.0:* ``timeout`` has incompatibly changed units from milliseconds to seconds.
-//|         The new upper limit on ``timeout`` is meant to catch mistaken use of milliseconds."""
+//|         The new upper limit on ``timeout`` is meant to catch mistaken use of milliseconds.
+//|
+//|         .. note:: RS485 support on i.MX and Raspberry Pi RP2040 is implemented in software.
+//|            The timing for the ``rs485_dir`` pin signal is done on a best-effort basis, and may not meet
+//|            RS485 specifications intermittently.
+//|         """
 //|         ...
 //|
 typedef struct {