From 6fec4e004c3953041f72fa717cec12a1c98264c5 Mon Sep 17 00:00:00 2001
From: Rahix <rahix@rahix.de>
Date: Thu, 26 Dec 2019 13:24:44 +0100
Subject: [PATCH] fix(ws2812): Fix first write making the first pixel green
The first epic_ws2812_write() call will set the first pixel to 0x008000
(bright green). This is caused by the GPIO line being pulled down on
mode-setting (epic_gpio_set_pin_mode). Wait before writing the values
to reset the bus and thus properly set the pixels to the correct colors
on first write.
Signed-off-by: Rahix <rahix@rahix.de>
---
epicardium/modules/ws2812.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/epicardium/modules/ws2812.c b/epicardium/modules/ws2812.c
index 9221b6a2..5fb48d53 100644
--- a/epicardium/modules/ws2812.c
+++ b/epicardium/modules/ws2812.c
@@ -63,14 +63,22 @@ void epic_ws2812_write(uint8_t pin, uint8_t *pixels, uint32_t n_bytes)
taskENTER_CRITICAL();
- epic_gpio_set_pin_mode(pin, EPIC_GPIO_MODE_OUT);
+ /*
+ * If the pin was not previously configured as an output, the
+ * `epic_gpio_set_pin_mode()` call will pull it down which the first
+ * neopixel interprets as the color `0x008000`. To fix this, wait a bit
+ * after mode-setting and then write the new values.
+ */
+ if ((epic_gpio_get_pin_mode(pin) & EPIC_GPIO_MODE_OUT) == 0) {
+ epic_gpio_set_pin_mode(pin, EPIC_GPIO_MODE_OUT);
+ }
+
+ GPIO_OutClr(pin_cfg);
+ epic_ws2812_delay_ticks(EPIC_WS2812_RESET_TCKS);
do {
epic_ws2812_transmit_byte(pin_cfg, *pixels);
} while (++pixels != pixels_end);
- GPIO_OutClr(pin_cfg);
- epic_ws2812_delay_ticks(EPIC_WS2812_RESET_TCKS);
-
taskEXIT_CRITICAL();
}
--
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