Hi,
On CYW943907AEVAL1F, interrupt latency sometimes getting longer.
Usually, it's approx 2-3us, but every 2-10 seconds get 30-100us.
In my project, CPU must respond within several microseconds.
Therefore this long latency is a issue to be solved.
How can I make the latency at around 3us constantly?
Sample program is attached.
Tools
- Windows 10 PC
- CYW943907AEVAL1F
- WICED-Studio 6.4.0.61 on Windows
- SocketTest v3.0 http://sockettest.sourceforge.net/
- Wi-Fi Access Point
- Jump wire 1pc
The connection diagram is shown below.
Usage
1) Power on Wi-Fi AP.
2) Using jump wire, connect J10.7 to J12.4 on CYW943907AEVAL1F.(J10.7=PWM4 output, J12.4=interrupt input)
3) Run SocketTest3 on Windows PC, it acts as a TCP Server.
4) Connect CYW943907AEVAL1F to Windows PC with USB cable.
5) Run TeraTerm, and connect CYW943907AEVAL1F via Serial port.
6) Type "join <AP SSID> wpa2_aes <Password>" on TeraTerm.
> join IoT-2G-01-1943 wpa2_aes PASSWORD
Joining : IoT-2G-01-1943
Successfully joined : IoT-2G-01-1943
Obtaining IPv4 address via DHCP
L1420 : dhcp_client_init() : DHCP CLIENT hostname = [WICED IP]
IPv4 network ready IP: 192.168.3.100
Setting IPv6 link-local address
IPv6 network ready IP: FE80:0000:0000:0000:A608:EAFF:FED9:CE58
7) Windows PC connects to the Wi-Fi AP.
😎 Set up SocketTest3 as a TCP Server. The IP address=X.X.X.X and Port=5001, and click "Start Listening".
9) Type "start -c X.X.X.X" on TereTerm, then start data transmission.
10) The interrupt latency information are displayed on TeraTerm.
exceed_cnt increments when exceeds threshold.
exceed_val shows interrupt interval when exceeds threshold.
> start -c 192.168.3.101 -n 100
wiced_tcp_connect start
> wlan_send_countdown=99, exceed_cnt=37, exceed_val=76100ns
wlan_send_countdown=98, exceed_cnt=37, exceed_val=76100ns
wlan_send_countdown=97, exceed_cnt=38, exceed_val=91250ns
wlan_send_countdown=96, exceed_cnt=38, exceed_val=91250ns
wlan_send_countdown=95, exceed_cnt=38, exceed_val=91250ns
wlan_send_countdown=94, exceed_cnt=38, exceed_val=91250ns
wlan_send_countdown=93, exceed_cnt=38, exceed_val=91250ns
wlan_send_countdown=92, exceed_cnt=39, exceed_val=91250ns
wlan_send_countdown=91, exceed_cnt=39, exceed_val=91250ns
wlan_send_countdown=90, exceed_cnt=41, exceed_val=75550ns
wlan_send_countdown=89, exceed_cnt=41, exceed_val=75550ns
wlan_send_countdown=88, exceed_cnt=41, exceed_val=75550ns
wlan_send_countdown=87, exceed_cnt=41, exceed_val=75550ns
wlan_send_countdown=86, exceed_cnt=42, exceed_val=91025ns
wlan_send_countdown=85, exceed_cnt=42, exceed_val=91025ns
...
wlan_send_countdown=3, exceed_cnt=55, exceed_val=75725ns
wlan_send_countdown=2, exceed_cnt=55, exceed_val=75725ns
wlan_send_countdown=1, exceed_cnt=56, exceed_val=75650ns
wlan_send_countdown=0, exceed_cnt=56, exceed_val=75650ns
Regards,
Nobuhiro
