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dpgeorgedpgeorge
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extmod/machine_i2c: Add i2c.writevto() that can write a vector of bufs.
For example: i2c.writevto(addr, (buf1, buf2)). This allows to efficiently (wrt memory) write data composed of separate buffers, such as a command followed by a large amount of data.
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‎extmod/machine_i2c.c‎

Lines changed: 47 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -480,6 +480,52 @@ STATIC mp_obj_t machine_i2c_writeto(size_t n_args, const mp_obj_t *args) {
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}
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STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_i2c_writeto_obj, 3, 4, machine_i2c_writeto);
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STATIC mp_obj_t machine_i2c_writevto(size_t n_args, const mp_obj_t *args) {
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mp_obj_base_t *self = (mp_obj_base_t*)MP_OBJ_TO_PTR(args[0]);
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mp_int_t addr = mp_obj_get_int(args[1]);
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// Get the list of data buffer(s) to write
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size_t nitems;
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const mp_obj_t *items;
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mp_obj_get_array(args[2], &nitems, (mp_obj_t**)&items);
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// Get the stop argument
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bool stop = (n_args == 3) ? true : mp_obj_is_true(args[3]);
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// Extract all buffer data, skipping zero-length buffers
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size_t alloc = nitems == 0 ? 1 : nitems;
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size_t nbufs = 0;
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mp_machine_i2c_buf_t *bufs = mp_local_alloc(alloc * sizeof(mp_machine_i2c_buf_t));
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for (; nitems--; ++items) {
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mp_buffer_info_t bufinfo;
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mp_get_buffer_raise(*items, &bufinfo, MP_BUFFER_READ);
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if (bufinfo.len > 0) {
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bufs[nbufs].len = bufinfo.len;
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bufs[nbufs++].buf = bufinfo.buf;
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}
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}
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// Make sure there is at least one buffer, empty if needed
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if (nbufs == 0) {
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bufs[0].len = 0;
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bufs[0].buf = NULL;
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nbufs = 1;
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}
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// Do the I2C transfer
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mp_machine_i2c_p_t *i2c_p = (mp_machine_i2c_p_t*)self->type->protocol;
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int ret = i2c_p->transfer(self, addr, nbufs, bufs, stop ? MP_MACHINE_I2C_FLAG_STOP : 0);
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mp_local_free(bufs);
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if (ret < 0) {
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mp_raise_OSError(-ret);
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}
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// Return number of acks received
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return MP_OBJ_NEW_SMALL_INT(ret);
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}
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STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(machine_i2c_writevto_obj, 3, 4, machine_i2c_writevto);
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STATIC int read_mem(mp_obj_t self_in, uint16_t addr, uint32_t memaddr, uint8_t addrsize, uint8_t *buf, size_t len) {
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mp_obj_base_t *self = (mp_obj_base_t*)MP_OBJ_TO_PTR(self_in);
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uint8_t memaddr_buf[4];
@@ -601,6 +647,7 @@ STATIC const mp_rom_map_elem_t machine_i2c_locals_dict_table[] = {
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{ MP_ROM_QSTR(MP_QSTR_readfrom), MP_ROM_PTR(&machine_i2c_readfrom_obj) },
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{ MP_ROM_QSTR(MP_QSTR_readfrom_into), MP_ROM_PTR(&machine_i2c_readfrom_into_obj) },
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{ MP_ROM_QSTR(MP_QSTR_writeto), MP_ROM_PTR(&machine_i2c_writeto_obj) },
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{ MP_ROM_QSTR(MP_QSTR_writevto), MP_ROM_PTR(&machine_i2c_writevto_obj) },
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// memory operations
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{ MP_ROM_QSTR(MP_QSTR_readfrom_mem), MP_ROM_PTR(&machine_i2c_readfrom_mem_obj) },

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