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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
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; struct gpio_dt_spec data_cmd;
#endif #endif
struct gpio_dt_spec reset; struct gpio_dt_spec reset;
int ready_time_ms;
}; };
struct ssd1306_data { struct ssd1306_data {
@ -403,6 +404,8 @@ static int ssd1306_init(const struct device *dev)
LOG_DBG(""); LOG_DBG("");
k_sleep(K_TIMEOUT_ABS_MS(config->ready_time_ms));
if (!ssd1306_bus_ready(dev)) { if (!ssd1306_bus_ready(dev)) {
LOG_ERR("Bus device %s not ready!", config->bus.bus->name); LOG_ERR("Bus device %s not ready!", config->bus.bus->name);
return -EINVAL; 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), 0, SPI_OP_MODE_MASTER | SPI_TRANSFER_MSB | SPI_WORD_SET(8), 0),
.data_cmd = GPIO_DT_SPEC_INST_GET(0, data_cmd_gpios), .data_cmd = GPIO_DT_SPEC_INST_GET(0, data_cmd_gpios),
#endif #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; 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. The RESET pin of SSD1306 is active low.
If connected directly the MCU pin should be configured If connected directly the MCU pin should be configured
as active low. 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.