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stmhal: Allow to set bits resolution for DAC; 8 is default, can have 12. 

This patch allows to configure the DAC resolution in the constructor and
in the init function, eg:

dac = DAC(1, bits=12).

The default resolution is 8 bits for backwards compatibility.  The bits
sets the maximum value accepted by write and write_timed methods, being
2**bits - 1.

When using write_timed with 12-bit resolution, the input buffer is
treated as an unsigned half-word array, typecode 'H'.

See PR #1130 for discussion.
This commit is contained in:
Damien George 2015-10-13 14:33:04 +01:00
parent b8f9ac5411
commit b5c43be135
2 changed files with 104 additions and 32 deletions
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35
docs/library/pyb.DAC.rst
View File

@ -15,6 +15,9 @@ Example usage::
dac = DAC(1) # create DAC 1 on pin X5
dac.write(128) # write a value to the DAC (makes X5 1.65V)
dac = DAC(1, bits=12) # use 12 bit resolution
dac.write(4095) # output maximum value, 3.3V
To output a continuous sine-wave::
import math
@ -29,21 +32,40 @@ To output a continuous sine-wave::
dac = DAC(1)
dac.write_timed(buf, 400 \* len(buf), mode=DAC.CIRCULAR)
To output a continuous sine-wave at 12-bit resolution::
import math
from array import array
from pyb import DAC
# create a buffer containing a sine-wave, using half-word samples
buf = array('H', 2048 + int(2047 * math.sin(2 * math.pi * i / 128)) for i in range(128))
# output the sine-wave at 400Hz
dac = DAC(1, bits=12)
dac.write_timed(buf, 400 \* len(buf), mode=DAC.CIRCULAR)
Constructors
------------
.. class:: pyb.DAC(port)
.. class:: pyb.DAC(port, bits=8)
Construct a new DAC object.
``port`` can be a pin object, or an integer (1 or 2).
DAC(1) is on pin X5 and DAC(2) is on pin X6.
``bits`` is an integer specifying the resolution, and can be 8 or 12.
The maximum value for the write and write_timed methods will be
2\*\*``bits``-1.
Methods
-------
.. method:: dac.init(bits=8)
Reinitialise the DAC. ``bits`` can be 8 or 12.
.. method:: dac.noise(freq)
Generate a pseudo-random noise signal. A new random sample is written
@ -57,13 +79,16 @@ Methods
.. method:: dac.write(value)
Direct access to the DAC output (8 bit only at the moment).
Direct access to the DAC output. The minimum value is 0. The maximum
value is 2\*\*``bits``-1, where ``bits`` is set when creating the DAC
object or by using the ``init`` method.
.. method:: dac.write_timed(data, freq, \*, mode=DAC.NORMAL)
Initiates a burst of RAM to DAC using a DMA transfer.
The input data is treated as an array of bytes (8 bit data).
The input data is treated as an array of bytes in 8-bit mode, and
an array of unsigned half-words (array typecode 'H') in 12-bit mode.
``freq`` can be an integer specifying the frequency to write the DAC
samples at, using Timer(6). Or it can be an already-initialised
Timer object which is used to trigger the DAC sample. Valid timers

101
stmhal/dac.c
View File

@ -139,9 +139,50 @@ typedef struct _pyb_dac_obj_t {
mp_obj_base_t base;
uint32_t dac_channel; // DAC_CHANNEL_1 or DAC_CHANNEL_2
DMA_Stream_TypeDef *dma_stream; // DMA1_Stream5 or DMA1_Stream6
pyb_dac_state_t state;
uint16_t pin; // GPIO_PIN_4 or GPIO_PIN_5
uint8_t bits; // 8 or 12
uint8_t state;
} pyb_dac_obj_t;
STATIC mp_obj_t pyb_dac_init_helper(pyb_dac_obj_t *self, mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
static const mp_arg_t allowed_args[] = {
{ MP_QSTR_bits, MP_ARG_INT, {.u_int = 8} },
};
// parse args
mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
// GPIO configuration
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.Pin = self->pin;
GPIO_InitStructure.Mode = GPIO_MODE_ANALOG;
GPIO_InitStructure.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOA, &GPIO_InitStructure);
// DAC peripheral clock
__DAC_CLK_ENABLE();
// stop anything already going on
HAL_DAC_Stop(&DAC_Handle, self->dac_channel);
if ((self->dac_channel == DAC_CHANNEL_1 && DAC_Handle.DMA_Handle1 != NULL)
|| (self->dac_channel == DAC_CHANNEL_2 && DAC_Handle.DMA_Handle2 != NULL)) {
HAL_DAC_Stop_DMA(&DAC_Handle, self->dac_channel);
}
// set bit resolution
if (args[0].u_int == 8 || args[0].u_int == 12) {
self->bits = args[0].u_int;
} else {
nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "unsupported bits"));
}
// reset state of DAC
self->state = DAC_STATE_RESET;
return mp_const_none;
}
// create the dac object
// currently support either DAC1 on X5 (id = 1) or DAC2 on X6 (id = 2)
@ -152,7 +193,7 @@ typedef struct _pyb_dac_obj_t {
/// DAC(1) is on pin X5 and DAC(2) is on pin X6.
STATIC mp_obj_t pyb_dac_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
// check arguments
mp_arg_check_num(n_args, n_kw, 1, 1, false);
mp_arg_check_num(n_args, n_kw, 1, MP_OBJ_FUN_ARGS_MAX, true);
// get pin/channel to output on
mp_int_t dac_id;
@ -172,42 +213,32 @@ STATIC mp_obj_t pyb_dac_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n
pyb_dac_obj_t *dac = m_new_obj(pyb_dac_obj_t);
dac->base.type = &pyb_dac_type;
uint32_t pin;
if (dac_id == 1) {
pin = GPIO_PIN_4;
dac->pin = GPIO_PIN_4;
dac->dac_channel = DAC_CHANNEL_1;
dac->dma_stream = DMA1_Stream5;
} else if (dac_id == 2) {
pin = GPIO_PIN_5;
dac->pin = GPIO_PIN_5;
dac->dac_channel = DAC_CHANNEL_2;
dac->dma_stream = DMA1_Stream6;
} else {
nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError, "DAC %d does not exist", dac_id));
}
// GPIO configuration
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.Pin = pin;
GPIO_InitStructure.Mode = GPIO_MODE_ANALOG;
GPIO_InitStructure.Pull = GPIO_NOPULL;
HAL_GPIO_Init(GPIOA, &GPIO_InitStructure);
// DAC peripheral clock
__DAC_CLK_ENABLE();
// stop anything already going on
HAL_DAC_Stop(&DAC_Handle, dac->dac_channel);
if ((dac->dac_channel == DAC_CHANNEL_1 && DAC_Handle.DMA_Handle1 != NULL)
|| (dac->dac_channel == DAC_CHANNEL_2 && DAC_Handle.DMA_Handle2 != NULL)) {
HAL_DAC_Stop_DMA(&DAC_Handle, dac->dac_channel);
}
dac->state = DAC_STATE_RESET;
// configure the peripheral
mp_map_t kw_args;
mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
pyb_dac_init_helper(dac, n_args - 1, args + 1, &kw_args);
// return object
return dac;
}
STATIC mp_obj_t pyb_dac_init(mp_uint_t n_args, const mp_obj_t *args, mp_map_t *kw_args) {
return pyb_dac_init_helper(args[0], n_args - 1, args + 1, kw_args);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_dac_init_obj, 1, pyb_dac_init);
#if defined(TIM6)
/// \method noise(freq)
/// Generate a pseudo-random noise signal. A new random sample is written
@ -280,7 +311,11 @@ STATIC mp_obj_t pyb_dac_write(mp_obj_t self_in, mp_obj_t val) {
self->state = DAC_STATE_WRITE_SINGLE;
}
HAL_DAC_SetValue(&DAC_Handle, self->dac_channel, DAC_ALIGN_8B_R, mp_obj_get_int(val));
// DAC output is always 12-bit at the hardware level, and we provide support
// for multiple bit "resolutions" simply by shifting the input value.
HAL_DAC_SetValue(&DAC_Handle, self->dac_channel, DAC_ALIGN_12B_R,
mp_obj_get_int(val) << (12 - self->bits));
HAL_DAC_Start(&DAC_Handle, self->dac_channel);
return mp_const_none;
@ -365,8 +400,13 @@ mp_obj_t pyb_dac_write_timed(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_
DMA_Handle.Init.Direction = DMA_MEMORY_TO_PERIPH;
DMA_Handle.Init.PeriphInc = DMA_PINC_DISABLE;
DMA_Handle.Init.MemInc = DMA_MINC_ENABLE;
DMA_Handle.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
DMA_Handle.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
if (self->bits == 8) {
DMA_Handle.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
DMA_Handle.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
} else {
DMA_Handle.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;
DMA_Handle.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;
}
DMA_Handle.Init.Mode = args[2].u_int;
DMA_Handle.Init.Priority = DMA_PRIORITY_HIGH;
DMA_Handle.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
@ -393,7 +433,13 @@ mp_obj_t pyb_dac_write_timed(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_
self->state = DAC_STATE_DMA_WAVEFORM + dac_trigger;
}
HAL_DAC_Start_DMA(&DAC_Handle, self->dac_channel, (uint32_t*)bufinfo.buf, bufinfo.len, DAC_ALIGN_8B_R);
if (self->bits == 8) {
HAL_DAC_Start_DMA(&DAC_Handle, self->dac_channel,
(uint32_t*)bufinfo.buf, bufinfo.len, DAC_ALIGN_8B_R);
} else {
HAL_DAC_Start_DMA(&DAC_Handle, self->dac_channel,
(uint32_t*)bufinfo.buf, bufinfo.len / 2, DAC_ALIGN_12B_R);
}
/*
// enable DMA stream
@ -417,6 +463,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_dac_write_timed_obj, 1, pyb_dac_write_time
STATIC const mp_map_elem_t pyb_dac_locals_dict_table[] = {
// instance methods
{ MP_OBJ_NEW_QSTR(MP_QSTR_init), (mp_obj_t)&pyb_dac_init_obj },
{ MP_OBJ_NEW_QSTR(MP_QSTR_write), (mp_obj_t)&pyb_dac_write_obj },
#if defined(TIM6)
{ MP_OBJ_NEW_QSTR(MP_QSTR_noise), (mp_obj_t)&pyb_dac_noise_obj },