diff --git a/src/hydrabus/hydrabus_mode_spi.c b/src/hydrabus/hydrabus_mode_spi.c
index a76be6eb..bd7022a1 100644
--- a/src/hydrabus/hydrabus_mode_spi.c
+++ b/src/hydrabus/hydrabus_mode_spi.c
@@ -38,8 +38,7 @@ static const char* str_bsp_init_err= { "bsp_spi_init() error %d\r\n" };
 
 #define MODE_DEV_NB_ARGC ((int)ARRAY_SIZE(mode_dev_arg)) /* Number of arguments/parameters for this mode */
 
-#define SPEED_NB (8)
-static uint32_t speeds[2][SPEED_NB] = {
+const uint32_t spi_speeds[2][SPI_SPEED_NB] = {
 	/* SPI1 */
 	{
 		320000,
@@ -91,14 +90,14 @@ static void show_params(t_hydra_console *con)
 		"floating",
 		proto->config.spi.dev_mode == DEV_MASTER ? "master" : "slave");
 
-	print_freq(con, speeds[proto->dev_num][proto->config.spi.dev_speed]);
+	print_freq(con, spi_speeds[proto->dev_num][proto->config.spi.dev_speed]);
 	cprintf(con, " (");
-	for (i = 0, cnt = 0; i < SPEED_NB; i++) {
+	for (i = 0, cnt = 0; i < SPI_SPEED_NB; i++) {
 		if (proto->config.spi.dev_speed == i)
 			continue;
 		if (cnt++)
 			cprintf(con, ", ");
-		print_freq(con, speeds[proto->dev_num][i]);
+		print_freq(con, spi_speeds[proto->dev_num][i]);
 	}
 	cprintf(con, ")\r\n");
 	cprintf(con, "Polarity: %d\r\nPhase: %d\r\nBit order: %s first\r\n",
@@ -187,8 +186,8 @@ static int exec(t_hydra_console *con, t_tokenline_parsed *p, int token_pos)
 		case T_FREQUENCY:
 			t += 2;
 			memcpy(&arg_float, p->buf + p->tokens[t], sizeof(float));
-			for (i = 0; i < SPEED_NB; i++) {
-				if (arg_float == speeds[proto->dev_num][i]) {
+			for (i = 0; i < SPI_SPEED_NB; i++) {
+				if (arg_float == spi_speeds[proto->dev_num][i]) {
 					proto->config.spi.dev_speed = i;
 					break;
 				}
diff --git a/src/hydrabus/hydrabus_mode_spi.h b/src/hydrabus/hydrabus_mode_spi.h
index aa2b4a55..3da0cbf0 100644
--- a/src/hydrabus/hydrabus_mode_spi.h
+++ b/src/hydrabus/hydrabus_mode_spi.h
@@ -26,5 +26,7 @@ enum {
 	SPI_LSB_FIRST,
 };
 
-#endif /* _HYDRABUS_MODE_SPI_H_ */
+#define SPI_SPEED_NB (8)
+extern const uint32_t spi_speeds[2][SPI_SPEED_NB];
 
+#endif /* _HYDRABUS_MODE_SPI_H_ */
diff --git a/src/hydrabus/hydrabus_serprog.c b/src/hydrabus/hydrabus_serprog.c
index f6e29cd8..1f0e01e7 100644
--- a/src/hydrabus/hydrabus_serprog.c
+++ b/src/hydrabus/hydrabus_serprog.c
@@ -22,6 +22,7 @@
 
 #include "hydrabus_bbio.h"
 #include "hydrabus_serprog.h"
+#include "hydrabus_mode_spi.h"
 #include "bsp_spi.h"
 
 void bbio_serprog_init_proto_default(t_hydra_console *con)
@@ -148,8 +149,35 @@ void bbio_mode_serprog(t_hydra_console *con)
 				break;
 			case S_CMD_S_SPI_FREQ:
 				chnRead(con->sdu, rx_data, 4);
-				//TODO: define variable speed.
+				/* requested speed */
+				to_rx = ((uint32_t)rx_data[3] << 24) | \
+				        ((uint32_t)rx_data[2] << 16) | \
+				        ((uint32_t)rx_data[1] << 8)  | rx_data[0];
+				/* value 0 is reserved and should not be requested as speed */
+				if (to_rx == 0) {
+					cprint(con, S_NAK, 1);
+					break;
+				}
+				/* find available SPI speed <= request speed */
+				i = 0;
+				while (i < SPI_SPEED_NB && spi_speeds[proto->dev_num][i] <= to_rx) {
+					i++;
+				}
+				i = i == 0 ? 0 : i - 1;
+				/* configure selected speed */
+				proto->config.spi.dev_speed = i;
+				if (bsp_spi_init(proto->dev_num, proto) != BSP_OK) {
+					cprint(con, S_NAK, 1);
+					break;
+				}
+				/* send back selected speed */
+				to_tx = spi_speeds[proto->dev_num][i];
+				tx_data[0] = (uint8_t)((to_tx >> 0 ) & 0xff);
+				tx_data[1] = (uint8_t)((to_tx >> 8 ) & 0xff);
+				tx_data[2] = (uint8_t)((to_tx >> 16) & 0xff);
+				tx_data[3] = (uint8_t)((to_tx >> 24) & 0xff);
 				cprint(con, S_ACK, 1);
+				cprint(con, (char *)tx_data, 4);
 				break;
 			case S_CMD_S_PIN_STATE:
 				chnRead(con->sdu, rx_data, 1);