From e7693b870063d87f70eff132c502dc40582cd4ae Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Martin=20Pomezn=C3=BD?= Date: Sat, 30 Dec 2017 00:05:56 +0100 Subject: [PATCH] GPIO2 note updated Updated note on GPIO2 with informations about possible pull-down resistor. Merges https://github.com/espressif/esp-idf/pull/1451 --- examples/storage/sd_card/README.md | 2 ++ 1 file changed, 2 insertions(+) diff --git a/examples/storage/sd_card/README.md b/examples/storage/sd_card/README.md index 341f3fe12..bfa2c5d80 100644 --- a/examples/storage/sd_card/README.md +++ b/examples/storage/sd_card/README.md @@ -37,6 +37,8 @@ With the given pinout for SPI mode, same connections between the SD card and ESP GPIO2 pin is used as a bootstrapping pin, and should be low to enter UART download mode. One way to do this is to connect GPIO0 and GPIO2 using a jumper, and then the auto-reset circuit on most development boards will pull GPIO2 low along with GPIO0, when entering download mode. +- Some boards have pulldown and/or LED on GPIO2. LED is usually ok, but pulldown will interfere with D0 signals and must be removed. Check the schematic of your development board for anything connected to GPIO2. + ### Note about GPIO12 GPIO12 is used as a bootstrapping pin to select output voltage of an internal regulator which powers the flash chip (VDD_SDIO). This pin has an internal pulldown so if left unconnected it will read low at reset (selecting default 3.3V operation). When adding a pullup to this pin for SD card operation, consider the following: