diff options
| -rw-r--r-- | docs/library/pyb.CAN.rst | 29 | ||||
| -rw-r--r-- | stmhal/can.c | 14 | ||||
| -rw-r--r-- | stmhal/qstrdefsport.h | 3 |
3 files changed, 33 insertions, 13 deletions
diff --git a/docs/library/pyb.CAN.rst b/docs/library/pyb.CAN.rst index 9ee5a0a695..094d263628 100644 --- a/docs/library/pyb.CAN.rst +++ b/docs/library/pyb.CAN.rst @@ -44,9 +44,32 @@ Methods Initialise the CAN bus with the given parameters: - ``mode`` is one of: NORMAL, LOOPBACK, SILENT, SILENT_LOOPBACK - - If ``extframe`` is True then the bus uses extended identifiers in the frames (29 bits). - Otherwise it uses standard 11 bit identifiers. + - if ``extframe`` is True then the bus uses extended identifiers in the frames + (29 bits); otherwise it uses standard 11 bit identifiers + - ``prescaler`` is used to set the duration of 1 time quanta; the time quanta + will be the input clock (PCLK1, see :meth:`pyb.freq()`) divided by the prescaler + - ``sjw`` is the resynchronisation jump width in units of the time quanta; + it can be 1, 2, 3, 4 + - ``bs1`` defines the location of the sample point in units of the time quanta; + it can be between 1 and 1024 inclusive + - ``bs2`` defines the location of the transmit point in units of the time quanta; + it can be between 1 and 16 inclusive + + The time quanta tq is the basic unit of time for the CAN bus. tq is the CAN + prescaler value divided by PCLK1 (the frequency of internal peripheral bus 1); + see :meth:`pyb.freq()` to determine PCLK1. + + A single bit is made up of the synchronisation segment, which is always 1 tq. + Then follows bit segment 1, then bit segment 2. The sample point is after bit + segment 1 finishes. The transmit point is after bit segment 2 finishes. + The baud rate will be 1/bittime, where the bittime is 1 + BS1 + BS2 multiplied + by the time quanta tq. + + For example, with PCLK1=42MHz, prescaler=100, sjw=1, bs1=6, bs2=8, the value of + tq is 2.38 microseconds. The bittime is 35.7 microseconds, and the baudrate + is 28kHz. + + See page 680 of the STM32F405 datasheet for more details. .. method:: can.deinit() diff --git a/stmhal/can.c b/stmhal/can.c index de1ef3ecd9..4b06b13eda 100644 --- a/stmhal/can.c +++ b/stmhal/can.c @@ -162,21 +162,15 @@ STATIC void pyb_can_print(void (*print)(void *env, const char *fmt, ...), void * } } -/// \method init(mode, extframe=False, prescaler=100, *, sjw=1, bs1=6, bs2=8) -/// -/// Initialise the CAN bus with the given parameters: -/// -/// - `mode` is one of: NORMAL, LOOPBACK, SILENT, SILENT_LOOPBACK +// init(mode, extframe=False, prescaler=100, *, sjw=1, bs1=6, bs2=8) STATIC mp_obj_t pyb_can_init_helper(pyb_can_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_mode, MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = CAN_MODE_NORMAL} }, { MP_QSTR_extframe, MP_ARG_BOOL, {.u_bool = false} }, { MP_QSTR_prescaler, MP_ARG_INT, {.u_int = 100} }, - /* { MP_QSTR_sjw, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1} }, { MP_QSTR_bs1, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 6} }, { MP_QSTR_bs2, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 8} }, - */ }; // parse args @@ -190,9 +184,9 @@ STATIC mp_obj_t pyb_can_init_helper(pyb_can_obj_t *self, mp_uint_t n_args, const CAN_InitTypeDef *init = &self->can.Init; init->Mode = args[0].u_int << 4; // shift-left so modes fit in a small-int init->Prescaler = args[2].u_int; - init->SJW = CAN_SJW_1TQ; // TODO set from args - init->BS1 = CAN_BS1_6TQ; // TODO set from args - init->BS2 = CAN_BS2_8TQ; // TODO set from args + init->SJW = ((args[3].u_int - 1) & 3) << 24; + init->BS1 = ((args[4].u_int - 1) & 0xf) << 16; + init->BS2 = ((args[5].u_int - 1) & 7) << 20; init->TTCM = DISABLE; init->ABOM = DISABLE; init->AWUM = DISABLE; diff --git a/stmhal/qstrdefsport.h b/stmhal/qstrdefsport.h index fc7942689c..e7ef1ef297 100644 --- a/stmhal/qstrdefsport.h +++ b/stmhal/qstrdefsport.h @@ -171,6 +171,9 @@ Q(addr) Q(fifo) Q(timeout) Q(extframe) +Q(sjw) +Q(bs1) +Q(bs2) Q(NORMAL) Q(LOOPBACK) Q(SILENT) |