diff --git a/rp_clockgen/README.md b/rp_clockgen/README.md
index 288c71c..18fb7a5 100644
--- a/rp_clockgen/README.md
+++ b/rp_clockgen/README.md
@@ -5,12 +5,13 @@ Clock generator sample code.
 
 Connect follow pins to external devices.  
 * pin 7 GPCLK0(GPIO4/ALT0)  
-* pin29 GPCLK1(GPIO5/ALT0)  
 * pin31 GPCLK2(GPIO6/ALT0)  
 
 If you can run this program,  
 RPi can supply clock to external device.  
 
+Don't use GPCLK1 (it's probably used for the Ethernet clock).  
+
 -----
 
 For Raspberry Pi Zero/1/2/3 Bare Metal code by AZO.  
diff --git a/rp_pcm/README.md b/rp_pcm/README.md
index d319ba3..ba01850 100644
--- a/rp_pcm/README.md
+++ b/rp_pcm/README.md
@@ -6,6 +6,7 @@ This is PCM/I2S sample code.
 You need any external I2S DAC board.  
 
 Connect I2S DAC board to below pins.  
+* pin 7 - GPCLK0   (GPIO04/ALT0), MCLK/SCLK  
 * pin12 - PCM_CLK  (GPIO18/ALT0), BCK/BCLK/BITCLK  
 * pin35 - PCM_FR   (GPIO19/ALT0), LRCK  
 * pin40 - PCM_DOUT (GPIO21/ALT0), Data  
diff --git a/rp_pcm_dma/README.md b/rp_pcm_dma/README.md
index ef3bf2b..202e50b 100644
--- a/rp_pcm_dma/README.md
+++ b/rp_pcm_dma/README.md
@@ -6,6 +6,7 @@ This is PCM/I2S with DMA sample code.
 You need any external I2S DAC board.  
 
 Connect I2S DAC board to below pins.  
+* pin 7 - GPCLK0   (GPIO04/ALT0), MCLK/SCLK  
 * pin12 - PCM_CLK  (GPIO18/ALT0), BCK/BCLK/BITCLK  
 * pin35 - PCM_FR   (GPIO19/ALT0), LRCK  
 * pin40 - PCM_DOUT (GPIO21/ALT0), Data