Hi all,

I am trying to use hardware flow control on HL6528G-2.8V FW version 8.10 (same issue on FW V3.0 and HL6528RD with latest firmware)

When I activate AT&K3 (use hardware flow control)

RTS line controls modem just fine when I receive large data but when I send large data (>1500bytes) by AT+KUDPSEND command CTS never signals to stop sending (goes to electrical 2.8V) just stays at 0volts all the time, actually it never changes state after normal power up sequence when it goes from electrical 2.8V to 0V.

I checked this with multiple modules and multiple boards including Sierra Wireless development board and also new HL6528RD module with latest FW

Is there known issue with CTS line on HL6528 series or am I using it wrong

Can you write short description when CTS line will control on incoming large amount of data?


Is it possible that nobody uses HW flow control ?

It is great feature and in AT command datasheet under KUDPSND command states that:

“Before using this command, it is highly recommended
to configure the module for Hardware flow control,
using the command AT&K3”

But I cant get CTS to notify when buffer is full.


Any news with this? We are having the exact same problem with the HL8548 but using KHTTPSPOST command instead (I am not sure that makes any difference. The HL never lowers its RTS pin, we overflow the buffer and the HL stops working.

Any help?