*/*spi.c

*/*spi.h

Support for odd bit lengths in SPI, per discussion at micropython#5225

Author: MrSurly

drivers/bus/softspi.c

@@ -4,6 +4,7 @@
  * The MIT License (MIT)
  *
  * Copyright (c) 2016-2018 Damien P. George
+ * Copyright (c) 2019 "Eric Poulsen" <eric@zyxod.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -25,6 +26,7 @@
  */
 
 #include "drivers/bus/spi.h"
+#include "py/runtime.h"
 
 int mp_soft_spi_ioctl(void *self_in, uint32_t cmd) {
     mp_soft_spi_obj_t *self = (mp_soft_spi_obj_t*)self_in;
@@ -44,38 +46,63 @@ int mp_soft_spi_ioctl(void *self_in, uint32_t cmd) {
     return 0;
 }
 
-void mp_soft_spi_transfer(void *self_in, size_t len, const uint8_t *src, uint8_t *dest) {
+void mp_soft_spi_transfer(void *self_in, size_t len, const uint8_t *src, uint8_t *dest, uint8_t bits) {
     mp_soft_spi_obj_t *self = (mp_soft_spi_obj_t*)self_in;
     uint32_t delay_half = self->delay_half;
 
+    bits = bits ? bits : self->bits;
+    if (bits == 0) {
+        // Shoudln't be possible with soft SPI, but
+        // just in case.
+        mp_raise_ValueError("bits cannot be 0");
+    }
+
+    int bytesPerChunk = (bits + 7) / 8;
+    // round length down as needed (possibly to zero)
+    len = len / bytesPerChunk * bytesPerChunk;
+    if(len == 0) {
+        return;
+    }
+
+    uint8_t remBits = bits;
+
     // only MSB transfer is implemented
 
     // If a port defines MICROPY_HW_SOFTSPI_MIN_DELAY, and the configured
     // delay_half is equal to this value, then the software SPI implementation
     // will run as fast as possible, limited only by CPU speed and GPIO time.
     #ifdef MICROPY_HW_SOFTSPI_MIN_DELAY
-    if (delay_half == MICROPY_HW_SOFTSPI_MIN_DELAY) {
-        for (size_t i = 0; i < len; ++i) {
-            uint8_t data_out = src[i];
+    if (delay_half == MICROPY_HW_SOFTSPI_MIN_DELAY)
+    {
+        while (len--) {
+            uint8_t bitsThisByte = remBits < 8 ? remBits : 8;
+            uint8_t data_out = *src++;
             uint8_t data_in = 0;
-            for (int j = 0; j < 8; ++j, data_out <<= 1) {
+
+            remBits -= bitsThisByte;
+            for (; bitsThisByte; --bitsThisByte, data_out <<= 1) {
                 mp_hal_pin_write(self->mosi, (data_out >> 7) & 1);
                 mp_hal_pin_write(self->sck, 1 - self->polarity);
                 data_in = (data_in << 1) | mp_hal_pin_read(self->miso);
                 mp_hal_pin_write(self->sck, self->polarity);
             }
+            remBits = remBits ? remBits : bits;
             if (dest != NULL) {
-                dest[i] = data_in;
+                *dest++ = data_in;
             }
         }
         return;
     }
-    #endif
+#endif
 
-    for (size_t i = 0; i < len; ++i) {
-        uint8_t data_out = src[i];
+
+    while(len--) {
+        uint8_t bitsThisByte = remBits < 8 ? remBits : 8;
+        uint8_t data_out = *src++;
         uint8_t data_in = 0;
-        for (int j = 0; j < 8; ++j, data_out <<= 1) {
+
+        remBits -= bitsThisByte;
+        for(;bitsThisByte; --bitsThisByte, data_out <<= 1) {
             mp_hal_pin_write(self->mosi, (data_out >> 7) & 1);
             if (self->phase == 0) {
                 mp_hal_delay_us_fast(delay_half);
@@ -93,8 +120,9 @@ void mp_soft_spi_transfer(void *self_in, size_t len, const uint8_t *src, uint8_t
                 mp_hal_delay_us_fast(delay_half);
             }
         }
+        remBits = remBits ? remBits : bits;
         if (dest != NULL) {
-            dest[i] = data_in;
+            *dest++ = data_in;
         }
     }
 }

drivers/bus/spi.h

@@ -35,13 +35,14 @@ enum {
 
 typedef struct _mp_spi_proto_t {
     int (*ioctl)(void *self, uint32_t cmd);
-    void (*transfer)(void *self, size_t len, const uint8_t *src, uint8_t *dest);
+    void (*transfer)(void *self, size_t len, const uint8_t *src, uint8_t *dest, uint8_t bits);
 } mp_spi_proto_t;
 
 typedef struct _mp_soft_spi_obj_t {
     uint32_t delay_half; // microsecond delay for half SCK period
     uint8_t polarity;
     uint8_t phase;
+    uint8_t bits;
     mp_hal_pin_obj_t sck;
     mp_hal_pin_obj_t mosi;
     mp_hal_pin_obj_t miso;
@@ -50,6 +51,6 @@ typedef struct _mp_soft_spi_obj_t {
 extern const mp_spi_proto_t mp_soft_spi_proto;
 
 int mp_soft_spi_ioctl(void *self, uint32_t cmd);
-void mp_soft_spi_transfer(void *self, size_t len, const uint8_t *src, uint8_t *dest);
+void mp_soft_spi_transfer(void *self, size_t len, const uint8_t *src, uint8_t *dest, uint8_t bits);
 
 #endif // MICROPY_INCLUDED_DRIVERS_BUS_SPI_H

drivers/memory/spiflash.c

@@ -75,7 +75,7 @@ STATIC void mp_spiflash_write_cmd_data(mp_spiflash_t *self, uint8_t cmd, size_t
     if (c->bus_kind == MP_SPIFLASH_BUS_SPI) {
         // Note: len/data are unused for standard SPI
         mp_hal_pin_write(c->bus.u_spi.cs, 0);
-        c->bus.u_spi.proto->transfer(c->bus.u_spi.data, 1, &cmd, NULL);
+        c->bus.u_spi.proto->transfer(c->bus.u_spi.data, 1, &cmd, NULL, 8);
         mp_hal_pin_write(c->bus.u_spi.cs, 1);
     } else {
         c->bus.u_qspi.proto->write_cmd_data(c->bus.u_qspi.data, cmd, len, data);
@@ -110,8 +110,8 @@ STATIC uint32_t mp_spiflash_read_cmd(mp_spiflash_t *self, uint8_t cmd, size_t le
     if (c->bus_kind == MP_SPIFLASH_BUS_SPI) {
         uint32_t buf;
         mp_hal_pin_write(c->bus.u_spi.cs, 0);
-        c->bus.u_spi.proto->transfer(c->bus.u_spi.data, 1, &cmd, NULL);
-        c->bus.u_spi.proto->transfer(c->bus.u_spi.data, len, (void*)&buf, (void*)&buf);
+        c->bus.u_spi.proto->transfer(c->bus.u_spi.data, 1, &cmd, NULL, 8);
+        c->bus.u_spi.proto->transfer(c->bus.u_spi.data, len, (void*)&buf, (void*)&buf, 8);
         mp_hal_pin_write(c->bus.u_spi.cs, 1);
         return buf;
     } else {

extmod/machine_spi.c

@@ -68,41 +68,50 @@ STATIC void mp_machine_spi_transfer(mp_obj_t self, size_t len, const void *src,
 STATIC mp_obj_t mp_machine_spi_read(size_t n_args, const mp_obj_t *args) {
     vstr_t vstr;
     vstr_init_len(&vstr, mp_obj_get_int(args[1]));
-    memset(vstr.buf, n_args == 3 ? mp_obj_get_int(args[2]) : 0, vstr.len);
-    mp_machine_spi_transfer(args[0], vstr.len, vstr.buf, vstr.buf);
+    memset(vstr.buf, n_args >= 3 ? mp_obj_get_int(args[2]) : 0, vstr.len);
+    uint8_t bits = n_args == 4 ? mp_obj_get_int(args[3]) : 0;
+    mp_machine_spi_transfer(args[0], vstr.len, vstr.buf, vstr.buf, bits);
     return mp_obj_new_str_from_vstr(&mp_type_bytes, &vstr);
 }
-MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_read_obj, 2, 3, mp_machine_spi_read);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_read_obj, 2, 4, mp_machine_spi_read);
 
 STATIC mp_obj_t mp_machine_spi_readinto(size_t n_args, const mp_obj_t *args) {
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);
-    memset(bufinfo.buf, n_args == 3 ? mp_obj_get_int(args[2]) : 0, bufinfo.len);
-    mp_machine_spi_transfer(args[0], bufinfo.len, bufinfo.buf, bufinfo.buf);
+    memset(bufinfo.buf, n_args >= 3 ? mp_obj_get_int(args[2]) : 0, bufinfo.len);
+    uint8_t bits = n_args == 4 ? mp_obj_get_int(args[3]) : 0;
+    mp_machine_spi_transfer(args[0], bufinfo.len, bufinfo.buf, bufinfo.buf, bits);
     return mp_const_none;
 }
-MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_readinto_obj, 2, 3, mp_machine_spi_readinto);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_readinto_obj, 2, 4, mp_machine_spi_readinto);
 
-STATIC mp_obj_t mp_machine_spi_write(mp_obj_t self, mp_obj_t wr_buf) {
+STATIC mp_obj_t mp_machine_spi_write(size_t n_args, const mp_obj_t *args) {
+    mp_obj_t self = args[0];
+    mp_obj_t wr_buf = args[1];
+    uint8_t bits = n_args == 3 ? mp_obj_get_int(args[2]) : 0;
     mp_buffer_info_t src;
     mp_get_buffer_raise(wr_buf, &src, MP_BUFFER_READ);
     mp_machine_spi_transfer(self, src.len, (const uint8_t *)src.buf, NULL);
     return mp_const_none;
 }
-MP_DEFINE_CONST_FUN_OBJ_2(mp_machine_spi_write_obj, mp_machine_spi_write);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_write_obj, 2, 3, mp_machine_spi_write);
 
-STATIC mp_obj_t mp_machine_spi_write_readinto(mp_obj_t self, mp_obj_t wr_buf, mp_obj_t rd_buf) {
+STATIC mp_obj_t mp_machine_spi_write_readinto(size_t n_args, const mp_obj_t *args) {
+    mp_obj_t self = args[0];
+    mp_obj_t wr_buf = args[1];
+    mp_obj_t rd_buf = args[2];
+    uint8_t bits = n_args == 4 ? mp_obj_get_int(args[3]) : 0;
     mp_buffer_info_t src;
     mp_get_buffer_raise(wr_buf, &src, MP_BUFFER_READ);
     mp_buffer_info_t dest;
     mp_get_buffer_raise(rd_buf, &dest, MP_BUFFER_WRITE);
     if (src.len != dest.len) {
         mp_raise_ValueError(MP_ERROR_TEXT("buffers must be the same length"));
     }
-    mp_machine_spi_transfer(self, src.len, src.buf, dest.buf);
+    mp_machine_spi_transfer(self, src.len, src.buf, dest.buf, bits);
     return mp_const_none;
 }
-MP_DEFINE_CONST_FUN_OBJ_3(mp_machine_spi_write_readinto_obj, mp_machine_spi_write_readinto);
+MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_write_readinto_obj, 3, 4, mp_machine_spi_write_readinto);
 
 STATIC const mp_rom_map_elem_t machine_spi_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&machine_spi_init_obj) },
@@ -179,8 +188,9 @@ STATIC mp_obj_t mp_machine_soft_spi_make_new(const mp_obj_type_t *type, size_t n
     self->spi.delay_half = baudrate_to_delay_half(args[ARG_baudrate].u_int);
     self->spi.polarity = args[ARG_polarity].u_int;
     self->spi.phase = args[ARG_phase].u_int;
-    if (args[ARG_bits].u_int != 8) {
-        mp_raise_ValueError(MP_ERROR_TEXT("bits must be 8"));
+    self->spi.bits = args[ARG_bits].u_int;
+    if (self->spi.bits == 0) {
+        mp_raise_ValueError("bits must be > 0");
     }
     if (args[ARG_firstbit].u_int != MICROPY_PY_MACHINE_SPI_MSB) {
         mp_raise_ValueError(MP_ERROR_TEXT("firstbit must be MSB"));

extmod/machine_spi.h

@@ -47,7 +47,7 @@
 typedef struct _mp_machine_spi_p_t {
     void (*init)(mp_obj_base_t *obj, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args);
     void (*deinit)(mp_obj_base_t *obj); // can be NULL
-    void (*transfer)(mp_obj_base_t *obj, size_t len, const uint8_t *src, uint8_t *dest);
+    void (*transfer)(mp_obj_base_t *obj, size_t len, const uint8_t *src, uint8_t *dest, uint8_t bits);
 } mp_machine_spi_p_t;
 
 typedef struct _mp_machine_soft_spi_obj_t {
@@ -60,10 +60,9 @@ extern const mp_obj_type_t mp_machine_soft_spi_type;
 extern const mp_obj_dict_t mp_machine_spi_locals_dict;
 
 mp_obj_t mp_machine_spi_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args);
-
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_read_obj);
 MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_readinto_obj);
-MP_DECLARE_CONST_FUN_OBJ_2(mp_machine_spi_write_obj);
-MP_DECLARE_CONST_FUN_OBJ_3(mp_machine_spi_write_readinto_obj);
+MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_write_obj);
+MP_DECLARE_CONST_FUN_OBJ_VAR_BETWEEN(mp_machine_spi_write_readinto_obj);
 
 #endif // MICROPY_INCLUDED_EXTMOD_MACHINE_SPI_H

ports/esp8266/machine_hspi.c

@@ -48,7 +48,7 @@ typedef struct _machine_hspi_obj_t {
     uint8_t phase;
 } machine_hspi_obj_t;
 
-STATIC void machine_hspi_transfer(mp_obj_base_t *self_in, size_t len, const uint8_t *src, uint8_t *dest) {
+STATIC void machine_hspi_transfer(mp_obj_base_t *self_in, size_t len, const uint8_t *src, uint8_t *dest, uint8_t bits) {
     (void)self_in;
 
     if (dest == NULL) {

ports/nrf/modules/machine/spi.c

@@ -151,7 +151,7 @@ STATIC int spi_find(mp_obj_t id) {
     }
 }
 
-void spi_transfer(const machine_hard_spi_obj_t * self, size_t len, const void * src, void * dest) {
+void spi_transfer(const machine_hard_spi_obj_t * self, size_t len, const void * src, void * dest, uint8_t bits) {
     nrfx_spi_xfer_desc_t xfer_desc = {
         .p_tx_buffer = src,
         .tx_length   = len,
@@ -377,9 +377,9 @@ STATIC void machine_hard_spi_deinit(mp_obj_t self_in) {
     nrfx_spi_uninit(self->p_spi);
 }
 
-STATIC void machine_hard_spi_transfer(mp_obj_base_t *self_in, size_t len, const uint8_t *src, uint8_t *dest) {
+STATIC void machine_hard_spi_transfer(mp_obj_base_t *self_in, size_t len, const uint8_t *src, uint8_t *dest, uint8_t bits) {
     const machine_hard_spi_obj_t *self = (machine_hard_spi_obj_t*)self_in;
-    spi_transfer(self, len, src, dest);
+    spi_transfer(self, len, src, dest, bits);
 }
 
 

ports/nrf/modules/machine/spi.h

@@ -33,4 +33,5 @@ void spi_init0(void);
 void spi_transfer(const machine_hard_spi_obj_t * self,
                   size_t                         len,
                   const void *                   src,
-                  void *                         dest);
+                  void *                         dest,
+                  uint8_t                        bits);

ports/nrf/mpconfigport.h

@@ -160,10 +160,6 @@
 #define MICROPY_PY_MACHINE_I2C      (0)
 #endif
 
-#ifndef MICROPY_PY_MACHINE_HW_SPI
-#define MICROPY_PY_MACHINE_HW_SPI   (1)
-#endif
-
 #ifndef MICROPY_PY_MACHINE_HW_PWM
 #define MICROPY_PY_MACHINE_HW_PWM   (0)
 #endif

ports/stm32/pyb_spi.c

@@ -190,7 +190,7 @@ STATIC mp_obj_t pyb_spi_send(size_t n_args, const mp_obj_t *pos_args, mp_map_t *
     pyb_buf_get_for_send(args[0].u_obj, &bufinfo, data);
 
     // send the data
-    spi_transfer(self->spi, bufinfo.len, bufinfo.buf, NULL, args[1].u_int);
+    spi_transfer(self->spi, bufinfo.len, bufinfo.buf, NULL, args[1].u_int, 8);
 
     return mp_const_none;
 }
@@ -292,7 +292,7 @@ STATIC mp_obj_t pyb_spi_send_recv(size_t n_args, const mp_obj_t *pos_args, mp_ma
     }
 
     // do the transfer
-    spi_transfer(self->spi, bufinfo_send.len, bufinfo_send.buf, bufinfo_recv.buf, args[2].u_int);
+    spi_transfer(self->spi, bufinfo_send.len, bufinfo_send.buf, bufinfo_recv.buf, args[2].u_int, 8);
 
     // return the received data
     if (o_ret != MP_OBJ_NULL) {