1. Stacking height either:

a. 1.5mm with mating connector (clearance under CM4 0mm): DF40C-100DS-0.4v

b. 3.0mm with mating connector (clearance under CM4 1.5mm): DF40HC(3.0)-100DS-0.4v

reference extra pins - https://docs.google.com/spreadsheets/d/1m27caMlk2gofswU9ZlBD_y3y81Y_0ARSmmQgm0i1AdQ/edit?gid=0#gid=0

pin definitions - cm4-datasheet.pdf - Chapter 4. Pinout

Understanding the Discrepancy

The Compute Module 4 Datasheet uses absolute pin numbering, which is sequential across both connectors (J6 and J7). Here's how it works:

  • Pins 1 to 100: Belong to J6 (Connector 1).
  • Pins 101 to 200: Belong to J7 (Connector 2).

Thus, Pin 164 corresponds to J7-77 (Connector 2, Top Row, Pin 77) when using the relative pin numbering scheme for the J7 connector.

Summary

  • HDMI1_CK_P is on J7 (Connector 2).
  • Its absolute pin number in the datasheet: 164.
  • Its relative pin number on J7: 77.

pin in pictures

use fun.L CONN.L CONN.R fun.R use
GND 2 1 GND
Ethernet_Pair1_P 4 3 Ethernet_Pair3_P
Ethernet_Pair1_N 6 5 Ethernet_Pair3_N
GND 8 7 GND
Ethernet_Pair0_N 10 9 Ethernet_Pair2_N
Ethernet_Pair0_P 12 11 Ethernet_Pair2_P
GND 14 13 GND
Ethernet_SYNC_IN(1.8V) 16 15 Ethernet_nLED3(3.3V)
Ethernet_SYNC_OUT(1.8V) 18 17 Ethernet_nLED2(3.3V)
EEPROM_nWP 20 19 Ethernet_nLED1(3.3V)
GND 22 21 Pi_nLED_Activity(3.3V)
GPIO26 24 23 GND
GPIO19 26 25 GPIO21
GPIO13 28 27 GPIO20
GPIO6 30 29 GPIO16
GND 32 31 GPIO12
GPIO5 34 33 GND
ID_SD 36 35 ID_SC
GPIO11 38 37 GPIO7
GPIO9 40 39 GPIO8
GND 42 41 GPIO25
GPIO10 44 43 GND
GPIO22 46 45 GPIO24
GPIO27 48 47 GPIO23
GPIO17 50 49 GPIO18
GND 52 51 GPIO15
GPIO4 54 53 GND
GPIO3 56 55 GPIO14
GPIO2 58 57 SD_CLK
GND 60 59 GND
SD_CMD 62 61 SD_DAT3
SD_DAT5 64 63 SD_DAT0
GND 66 65 GND
SD_DAT4 68 67 SD_DAT1
SD_DAT7 70 69 SD_DAT2
SD_DAT6 72 71 GND
GND 74 73 SD_VDD_Override
Reserved 76 75 SD_PWR_ON
GPIO_VREF 78 77 +5V_Input
SCL0 80 79 +5V_Input
SDA0 82 81 +5V_Input
+3V3_Output 84 83 +5V_Input
+3V3_Output 86 85 +5V_Input
+1.8V_output 88 87 +5V_Input
+1.8V_output 90 89 WL_nDisable
RUN_PG 92 91 BL_nDisable
AnalogIP1 94 93 nRPIBOOT
AnalogIP0 96 95 nPI_LED_PWR
GND 98 97 Camera_GPIO
nEXTRST 100 99 Global_EN

pin note

  • 28&29 are ethernet
  • 30-33 are Bluetooth
  • 34-39 are Wifi (SDIO)
  • 40, 41, and 43 are boot rom related.
  • 42 is the activity LED
  • 44&45 are I2C to the camera and display
  • 46&47 are internal control
  • 48-53 would appear to configured as SD card, but I believe you're right that they on dedicated pins.

ref

pin table

Pin Signal Description
1 GND Ground (0V)
2 GND Ground (0V)
3 Ethernet_Pair3_P Ethernet pair 3 positive (connect to transformer or MagJack)
4 Ethernet_Pair1_P Ethernet pair 1 positive (connect to transformer or MagJack)
5 Ethernet_Pair3_N Ethernet pair 3 negative (connect to transformer or MagJack)
6 Ethernet_Pair1_N Ethernet pair 1 negative (connect to transformer or MagJack)
7 GND Ground (0V)
8 GND Ground (0V)
9 Ethernet_Pair2_N Ethernet pair 2 negative (connect to transformer or MagJack)
10 Ethernet_Pair0_N Ethernet pair 0 negative (connect to transformer or MagJack)
11 Ethernet_Pair2_P Ethernet pair 2 positive (connect to transformer or MagJack)
12 Ethernet_Pair0_P Ethernet pair 0 positive (connect to transformer or MagJack)
13 GND Ground (0V)
14 GND Ground (0V)
15 Ethernet_nLED3 Active-low Ethernet activity indicator (CM4_3.3V signal): typically a green LED is connected to this pin. IOL = 8mA @ VOL < 0.4V
16 Ethernet_SYNC_IN IEEE1588 SYNC Input pin (CM4_3.3V signal: IOL = 8mA @ VOL < 0.4V)
17 Ethernet_nLED2 Active-low Ethernet speed indicator (CM4_3.3Vsignal): typically a yellow LED is connected to this pin. A low state indicates the 1Gbit or 100Mbit link: IOL = 8mA @ VOL < 0.4V
18 Ethernet_SYNC_OUT IEEE1588 SYNC Output pin (CM4_3.3V signal: IOL = 8mA @ VOL < 0.4V)
19 Ethernet_nLED1 Active-low Ethernet speed indicator (CM4_3.3V signal): typically a yellow LED is connected to this pin. A low state indicates the 1Gbit or 10Mbit link: IOL = 8mA @ VOL < 0.4V
20 EEPROM_nWP Leave floating NB internally pulled up to CM4_3.3V via 100kΩ (VIL < 0.8V), but can be grounded to prevent writing to the on-board EEPROM which stores the bootcode
21 Pi_nLED_Activity Active-low Pi activity LED. 20mA Max, 5V tolerant (VOL < 0.4V). (this is the signal that drives the green LED on the Raspberry Pi 4 Model B)
22 GND Ground (0V)
23 GND Ground (0V)
24 GPIO26 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
25 GPIO21 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
26 GPIO19 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
27 GPIO20 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
28 GPIO13 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
29 GPIO16 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
30 GPIO6 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
31 GPIO12 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
32 GND Ground (0V)
33 GND Ground (0V)
34 GPIO5 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
35 GPIO1 ID_SC (BCM2711 GPIO 1) GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
36 GPIO0 ID_SD (BCM2711 GPIO 0) GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
37 GPIO7 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
38 GPIO11 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
39 GPIO8 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
40 GPIO9 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
41 GPIO25 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
42 GND Ground (0V)
43 GND Ground (0V)
44 GPIO10 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
45 GPIO24 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
46 GPIO22 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
47 GPIO23 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
48 GPIO27 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
49 GPIO18 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
50 GPIO17 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
51 GPIO15 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
52 GND Ground (0V)
53 GND Ground (0V)
54 GPIO4 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
55 GPIO14 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V
56 GPIO3 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V. Internal 1.8kΩ pull up to GPIO_VREF
57 SD_CLK SD card clock signal (only available on CM4Lite)
58 GPIO2 GPIO: typically a 3.3V signal, but can be a 1.8V signal by connecting GPIO_VREF to CM4_1.8V. Internal 1.8kΩ pull up to GPIO_VREF
59 GND Ground (0V)
60 GND Ground (0V)
61 SD_DAT3 SD card/eMMC Data3 signal (only available on CM4Lite)
62 SD_CMD SD card/eMMC Command signal (only available on CM4Lite)
63 SD_DAT0 SD card/eMMC Data0 signal (only available on CM4Lite)
64 SD_DAT5 SD card/eMMC Data5 signal (only available on CM4Lite)
65 GND Ground (0V)
66 GND Ground (0V)
67 SD_DAT1 SD card/eMMC Data1 signal (only available on CM4Lite)
68 SD_DAT4 SD card/eMMC Data4 signal (only available on CM4Lite)
69 SD_DAT2 SD card/eMMC Data2 signal (only available on CM4Lite)
70 SD_DAT7 SD card/eMMC Data7 signal (only available on CM4Lite)
71 GND Ground (0V)
72 SD_DAT6 SD card/eMMC Data6 signal (only available on CM4Lite)
73 SD_VDD_OVERRIDE Connect to CM4_3.3V to force SD card/eMMC interface to 1.8V signalling instead of 3.3V, otherwise leave unconnected. Typically only used if external eMMC is connected.
74 GND Ground (0V)
75 SD_PWR_ON Output to power-switch for the SD card. The CM4 sets this pin high (3.3V) to signal that power to the SD card should be turned on. If booting from the SD card is required then a pullup should also be fitted so the power-switch defaults to on. (only available on CM4Lite)
76 Reserved Do not connect anything to this pin.
77 +5V (Input) 4.75V-5.25V. Main power input
78 GPIO_VREF Must be connected to CM4_3.3V (pins 84 and 86) for 3.3V GPIO or CM4_1.8V (pins 88 and 90) for 1.8V GPIO. This pin cannot be floating or connected to ground.
79 +5V (Input) 4.75V-5.25V. Main power input
80 GPIO45 SCL0 I2C clock pin (BCM2711 GPIO45): typically used for Camera and Display. Internal 1.8kΩ pull up to CM4_3.3V
81 +5V (Input) 4.75V-5.25V. Main power input
82 GPIO44 SDA0 I2C Data pin (BCM2711 GPIO44): typically used for Camera and Display. Internal 1.8kΩ pull up to CM4_3.3V
83 +5V (Input) 4.75V-5.25V. Main power input
84 CM4_3.3V (Output) 3.3V ± 2.5%. Power Output max 300mA per pin for a total of 600mA. This will be powered down during power-off or GLOBAL_EN being set low
85 +5V (Input) 4.75V-5.25V. Main power input
86 CM4_3.3V (Output) 3.3V ± 2.5%. Power Output max 300mA per pin for a total of 600mA. This will be powered down during power-off or GLOBAL_EN being set low
87 +5V (Input) 4.75V-5.25V. Main power input
88 CM4_1.8V (Output) 1.8V ± 2.5%. Power Output max 300mA per pin for a total of 600mA. This will be powered down during power-off or GLOBAL_EN being set low
89 WL_nDisable Can be left floating; if driven low the wireless interface will be disabled. Internally pulled up via 1.8kΩ to CM4_3.3V
90 CM4_1.8V (Output) 1.8V ± 2.5%. Power Output max 300mA per pin for a total of 600mA. This will be powered down during power-off or GLOBAL_EN being set low
91 BT_nDisable Can be left floating; if driven low the Bluetooth interface will be disabled. Internally pulled up via 1.8kΩ to CM4_3.3V
92 RUN_PG Bidirectional pin. Can be driven low (via a 220Ω resistor) to reset the CM4 CPU. As an output, a high signals that power is good and CPU is running. Internally pulled up to +3.3V via 10kΩ
93 nRPIBOOT A low on this pin forces booting from an RPI server (e.g. PC or a Raspberry Pi); if not used leave floating. Internally pulled up via 10kΩ to +3.3V
94 AnalogIP1 Analogue input of the MXL7704: typically connected to CC pin of Type C power connector
95 PI_LED_nPWR Active-low output to drive Power On LED. This signal needs to be buffered.
96 AnalogIP0 Analogue input of the MXL7704: typically connected to CC pin of Type C power connector
97 Camera_GPIO Typically used to shut down the camera to reduce power. Reassigning this pin to another function isn’t recommended. CM4_3.3V signalling
98 GND Ground (0V)
99 GLOBAL_EN Input. Drive low to power off CM4. Internally pulled up with a 100kΩ to +5V
100 nEXTRST Output. Driven low during reset; Driven high (CM4_3.3V) once CM4 CPU has started to boot
101 USB_OTG_ID Input (3.3V signal) USB OTG Pin. Internally pulled up. When grounded the CM4 becomes a USB host but the correct OS driver also needs to be used
102 PCIe_CLK_nREQ Input (3.3V signal) PCIe clock request pin (low to request PCI clock). Internally pulled up
103 USB_N USB D104 Reserved Do not connect anything to this pin.
105 USB_P USB D+
106 Reserved Do not connect anything to this pin.
107 GND Ground (0V)
108 GND Ground (0V)
109 PCIe_nRST Output (+3.3V signal) PCIe reset active-low
110 PCIe_CLK_P PCIe clock Out positive (100MHz) NB AC coupling capacitor included on CM4
111 VDAC_COMP Video DAC output (TV OUT)
112 PCIe_CLK_N PCIe clock Out negative (100MHz) NB AC coupling capacitor included on CM4
113 GND Ground (0V)
114 GND Ground (0V)
115 CAM1_D0_N Input Camera1 D0 negative
116 PCIe_RX_P Input PCIe GEN 2 RX positive NB external AC coupling capacitor required
117 CAM1_D0_P Input Camera1 D0 positive
118 PCIe_RX_N Input PCIe GEN 2 RX negative NB external AC coupling capacitor required
119 GND Ground (0V)
120 GND Ground (0V)
121 CAM1_D1_N Input Camera1 D1 negative
122 PCIe_TX_P Output PCIe GEN 2 TX positive NB AC coupling capacitor included on CM4
123 CAM1_D1_P Input Camera1 D1 positive
124 PCIe_TX_N Output PCIe GEN 2 TX positive NB AC coupling capacitor included on CM4
125 GND Ground (0V)
126 GND Ground (0V)
127 CAM1_C_N Input Camera1 clock negative
128 CAM0_D0_N Input Camera0 D0 negative
129 CAM1_C_P Input Camera1 clock positive
130 CAM0_D0_P Input Camera0 D0 positive
131 GND Ground (0V)
132 GND Ground (0V)
133 CAM1_D2_N Input Camera1 D2 negative
134 CAM0_D1_N Input Camera0 D1 negative
135 CAM1_D2_P Input Camera1 D2 positive
136 CAM0_D1_P Input Camera0 D1 positive
137 GND Ground (0V)
138 GND Ground (0V)
139 CAM1_D3_N Input Camera1 D3 negative
140 CAM0_C_N Input Camera0 clock negative
141 CAM1_D3_P Input Camera1 D3 positive
142 CAM0_C_P Input Camera0 clock positive
143 HDMI1_HOTPLUG Input HDMI1 hotplug. Internally pulled down with a 100kΩ. 5V tolerant. (It can be connected directly to a HDMI connector; a small amount of ESD protection is provided on the CM4 by an on-board HDMI05-CL02F3)
144 GND Ground (0V)
145 HDMI1_SDA Bidirectional HDMI1 SDA. Internally pulled up with a 1.8kΩ. 5V tolerant. (It can be connected directly to a HDMI connector; a small amount of ESD protection is provided on the CM4 by an on-board HDMI05-CL02F3)
146 HDMI1_TX2_P Output HDMI1 TX2 positive
147 HDMI1_SCL Bidirectional HDMI1 SCL. Internally pulled up with a 1.8kΩ. 5V tolerant. (It can beconnected directly to a HDMI connector; a small amount of ESD protection is provided onthe CM4 by an on-board HDMI05-CL02F3)
148 HDMI1_TX2_N Output HDMI1 TX2 negative
149 GPIO28 HDMI1_CEC Input HDMI1 CEC. Internally pulled up with a 27kΩ. 5V tolerant. (It can be connecteddirectly to a HDMI connector; a small amount of ESD protection is provided on the CM4by an on-board HDMI05-CL02F3)
150 GND Ground (0V)
151 HDMI0_CEC Input HDMI0 CEC. Internally pulled up with a 27kΩ. 5V tolerant (It can be connecteddirectly to a HDMI connector; a small amount of ESD protection is provided on the CM4by an on-board HDMI05-CL02F3)
152 HDMI1_TX1_P Output HDMI1 TX1 positive
153 HDMI0_HOTPLUG Input HDMI0 hotplug. Internally pulled down 100kΩ. 5V tolerant. (It can be connecteddirectly to a HDMI connector; a small amount of ESD protection is provided on the CM4by an on-board HDMI05-CL02F3)
154 HDMI1_TX1_N Output HDMI1 TX1 negative
155 GND Ground (0V)
156 GND Ground (0V)
157 DSI0_D0_N Output Display0 D0 negative
158 HDMI1_TX0_P Output HDMI1 TX0 positive
159 DSI0_D0_P Output Display0 D0 positive
160 HDMI1_TX0_N Output HDMI1 TX0 negative
161 GND Ground (0V)
162 GND Ground (0V)
163 DSI0_D1_N Output Display0 D1 negative
164 HDMI1_CLK_P Output HDMI1 clock positive
165 DSI0_D1_P Output Display0 D1 positive
166 HDMI1_CLK_N Output HDMI1 clock negative
167 GND Ground (0V)
168 GND Ground (0V)
169 DSI0_C_N Output Display0 clock negative
170 HDMI0_TX2_P Output HDMI0 TX2 positive
171 DSI0_C_P Output Display0 clock positive
172 HDMI0_TX2_N Output HDMI0 TX2 negative
173 GND Ground (0V)
174 GND Ground (0V)
175 DSI1_D0_N Output Display1 D0 negative
176 HDMI0_TX1_P Output HDMI0 TX1 positive
177 DSI1_D0_P Output Display1 D0 positive
178 HDMI0_TX1_N Output HDMI0 TX1 negative
179 GND Ground (0V)
180 GND Ground (0V)
181 DSI1_D1_N Output Display1 D1 negative
182 HDMI0_TX0_P Output HDMI0 TX0 positive
183 DSI1_D1_P Output Display1 D1 positive
184 HDMI0_TX0_N Output HDMI0 TX0 negative
185 GND Ground (0V)
186 GND Ground (0V)
187 DSI1_C_N Output Display1 clock negative
188 HDMI0_CLK_P Output HDMI0 clock positive
189 DSI1_C_P Output Display1 clock positive
190 HDMI0_CLK_N Output HDMI0 clock negative
191 GND Ground (0V)
192 GND Ground (0V)
193 DSI1_D2_N Output Display1 D2 negative
194 DSI1_D3_N Output Display1 D3 negative
195 DSI1_D2_P Output Display1 D2 positive
196 DSI1_D3_P Output Display1 D3 positive
197 GND Ground (0V)
198 GND Ground (0V)
199 HDMI0_SDA Bidirectional HDMI0 SDA. Internally pulled up with a 1.8kΩ. 5V tolerant. (It can be connected directly to a HDMI connector; a small amount of ESD protection is provided on the CM4 by an on-board HDMI05-CL02F3)
200 HDMI0_SCL Bidirectional HDMI0 SCL. Internally pulled up with a 1.8kΩ. 5V tolerant. (It can be connected directly to a HDMI connector; a small amount of ESD protection is provided on the CM4 by an on-board HDMI05-CL02F3)