Transmitting data via Bluetooth Serial as well as USB CDC Serial but not getting High data rates on U

[prithvi25]

Hello,

I want to send data via Bluetooth Serial as well as USB CDC Serial and currently, I am getting data rates up to 3.2KB/s on a Windows Laptop.

I read this https://devzone.nordicsemi.com/f/nordic-q-a/38822/usbd-with-cdc-acm-class-windows-10-maximum-data-rate 

where the team said that they had received 215 KB/s.

I tried the example code usb_cdc_acm and in that, I got about 85 KB/s.

Is there any example code to get about 215 KB/s data rates on USB CDC?

[Dmitry]

Hi,

On my Windows 10 system, the raw throughput of CDC ACM (without BLE connection), as long as I remember, shows 425 KB/s from PC to device. Certainly it depends on host, but USB CDC shouldn't be a bottleneck here. Are you using the latest SDK? If you're trying an usb_cdc_acm example, set READ_SIZE to at least 64 bytes and comment out NRF_LOG_INFO lines in RX handler.

[prithvi25]

After doing this I am getting about 98 KB/s from device to PC.

NOTE: I want to send data from nrf52480 to Windows Laptop via USB CDC Serial at 200 KB/s and also send the same data via BT.

[Dmitry]

prithvi25 said:

After doing this I am getting about 98 KB/s from device to PC.

As for me, it's too low... could you show your code? Maybe your terminal program is not optimized for high-speed transfers. It's better to write your own simple reader.

prithvi25 said:

I want to send data from nrf52480 to Windows Laptop via USB CDC Serial at 200 KB/s and also send the same data via BT.

I don't think it's possible. Maximum achievable troughput over BLE is ~1.4Mbps (175 KB/s), with simultaneous high load over USB bus there will be even slower results.

[prithvi25]

0407.usbd_cdc_acm.zip

I have attached my code. Currently, it only has a USB CDC Serial which gives a 98 KB/s data rate. if that can reach 200 KB/s or more then it also works for me.

[Dmitry]

app_usbd_cdc_acm_write() doesn't use any internal buffers, it passes your data directly to nrfx_usbd_ep_transfer() - each packet contains a short string instead of 64 bytes. Try to pass exactly 64 bytes in each write.