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display: ssd1306: add some init delay

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Seems like the SSD1306 controller needs a bit of time after power up
before it can take i2c commands. This causes problems with
microcontrollers that have no other delays in the startup sequence, like
rpi_pico.

There's currently no good way of modeling this in Zephyr right now, and
there's also no clear indication of how much time the device needs in
the datasheet that I could find, but it seems like 10ms is enough for
that to start reliably so add a delay in the ssd1306 init function to
ensure that at least that time has passed from system power up.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>
This commit is contained in:
Fabio Baltieri 2023-08-29 18:54:21 +01:00 committed by Carles Cufí
parent eacdadf270
commit 3d713a42e8
2 changed files with 13 additions and 1 deletions
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6
drivers/display/ssd1306.c
View file

@ -56,6 +56,7 @@ struct ssd1306_config {
struct gpio_dt_spec data_cmd;
#endif
struct gpio_dt_spec reset;
int ready_time_ms;
};
struct ssd1306_data {
@ -403,6 +404,8 @@ static int ssd1306_init(const struct device *dev)
LOG_DBG("");
k_sleep(K_TIMEOUT_ABS_MS(config->ready_time_ms));
if (!ssd1306_bus_ready(dev)) {
LOG_ERR("Bus device %s not ready!", config->bus.bus->name);
return -EINVAL;
@ -434,7 +437,8 @@ static const struct ssd1306_config ssd1306_config = {
0, SPI_OP_MODE_MASTER | SPI_TRANSFER_MSB | SPI_WORD_SET(8), 0),
.data_cmd = GPIO_DT_SPEC_INST_GET(0, data_cmd_gpios),
#endif
.reset = GPIO_DT_SPEC_INST_GET_OR(0, reset_gpios, { 0 })
.reset = GPIO_DT_SPEC_INST_GET_OR(0, reset_gpios, { 0 }),
.ready_time_ms = DT_INST_PROP(0, ready_time_ms),
};
static struct ssd1306_data ssd1306_driver;

8
dts/bindings/display/solomon,ssd1306fb-common.yaml
View file

@ -48,3 +48,11 @@ properties:
The RESET pin of SSD1306 is active low.
If connected directly the MCU pin should be configured
as active low.
ready-time-ms:
type: int
default: 10
description: |
Time it takes for the device from power up to become responsive and
accepting commands. Defaults to 10ms (found by trial and error) if not
provided.